diff --git a/src/sage/rings/commutative_algebra.py b/src/sage/rings/commutative_algebra.py
index 1e209e453c4..dce8c576a1d 100644
--- a/src/sage/rings/commutative_algebra.py
+++ b/src/sage/rings/commutative_algebra.py
@@ -2,7 +2,7 @@
 Abstract base class for commutative algebras
 """
 
-#*****************************************************************************
+# ***************************************************************************
 #       Copyright (C) 2005 William Stein <wstein@gmail.com>
 #
 #  Distributed under the terms of the GNU General Public License (GPL)
@@ -15,24 +15,6 @@
 #  The full text of the GPL is available at:
 #
 #                  https://www.gnu.org/licenses/
-#*****************************************************************************
+# ***************************************************************************
 
 from sage.categories.commutative_algebras import CommutativeAlgebras
-
-
-def is_CommutativeAlgebra(x):
-    """
-    Check to see if ``x`` is in the category of ``CommutativeAlgebras``.
-
-    EXAMPLES::
-
-        sage: from sage.rings.commutative_algebra import is_CommutativeAlgebra
-        sage: is_CommutativeAlgebra(QQ['x'])
-        doctest:warning...
-        DeprecationWarning: the function is_CommutativeAlgebra is deprecated; use '... in Algebras(base_ring).Commutative()' instead
-        See https://github.com/sagemath/sage/issues/35999 for details.
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(35999, "the function is_CommutativeAlgebra is deprecated; use '... in Algebras(base_ring).Commutative()' instead")
-    return x in CommutativeAlgebras(x.base_ring())
diff --git a/src/sage/rings/complex_double.pyx b/src/sage/rings/complex_double.pyx
index 43dd9951971..8a6a215174d 100644
--- a/src/sage/rings/complex_double.pyx
+++ b/src/sage/rings/complex_double.pyx
@@ -694,29 +694,6 @@ cdef ComplexDoubleElement new_ComplexDoubleElement():
     return z
 
 
-def is_ComplexDoubleElement(x):
-    """
-    Return ``True`` if ``x`` is a :class:`ComplexDoubleElement`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.complex_double import is_ComplexDoubleElement
-        sage: is_ComplexDoubleElement(0)
-        doctest:warning...
-        DeprecationWarning: The function is_ComplexDoubleElement is deprecated;
-        use 'isinstance(..., ComplexDoubleElement)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        False
-        sage: is_ComplexDoubleElement(CDF(0))
-        True
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_ComplexDoubleElement is deprecated; "
-                       "use 'isinstance(..., ComplexDoubleElement)' instead.")
-    return isinstance(x, ComplexDoubleElement)
-
-
 cdef class ComplexDoubleElement(FieldElement):
     """
     An approximation to a complex number using double precision
diff --git a/src/sage/rings/complex_interval.pyx b/src/sage/rings/complex_interval.pyx
index 1287c764bd0..0a1d10f05ea 100644
--- a/src/sage/rings/complex_interval.pyx
+++ b/src/sage/rings/complex_interval.pyx
@@ -74,29 +74,6 @@ from sage.rings.convert.mpfi cimport mpfi_set_sage
 from sage.rings.infinity import infinity
 
 
-def is_ComplexIntervalFieldElement(x):
-    """
-    Check if ``x`` is a :class:`ComplexIntervalFieldElement`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.complex_interval import is_ComplexIntervalFieldElement as is_CIFE
-        sage: is_CIFE(CIF(2))
-        doctest:warning...
-        DeprecationWarning: The function is_ComplexIntervalFieldElement is deprecated;
-        use 'isinstance(..., ComplexIntervalFieldElement)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_CIFE(CC(2))
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_ComplexIntervalFieldElement is deprecated; "
-                       "use 'isinstance(..., ComplexIntervalFieldElement)' instead.")
-    return isinstance(x, ComplexIntervalFieldElement)
-
-
 cdef class ComplexIntervalFieldElement(FieldElement):
     """
     A complex interval.
diff --git a/src/sage/rings/complex_mpfr.pyx b/src/sage/rings/complex_mpfr.pyx
index 6ca1c628806..95c254dba2e 100644
--- a/src/sage/rings/complex_mpfr.pyx
+++ b/src/sage/rings/complex_mpfr.pyx
@@ -119,46 +119,6 @@ def set_global_complex_round_mode(n):
     rnd = n
 
 
-def is_ComplexNumber(x):
-    r"""
-    Return ``True`` if ``x`` is a complex number. In particular, if ``x`` is
-    of the :class:`ComplexNumber` type.
-
-    EXAMPLES::
-
-        sage: from sage.rings.complex_mpfr import is_ComplexNumber
-        sage: a = ComplexNumber(1, 2); a
-        1.00000000000000 + 2.00000000000000*I
-        sage: is_ComplexNumber(a)
-        doctest:warning...
-        DeprecationWarning: The function is_ComplexNumber is deprecated;
-        use 'isinstance(..., ComplexNumber)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: b = ComplexNumber(1); b
-        1.00000000000000
-        sage: is_ComplexNumber(b)
-        True
-
-    Note that the global element ``I`` is a number field element, of type
-    :class:`sage.rings.number_field.number_field_element_quadratic.NumberFieldElement_gaussian`,
-    while elements of the class :class:`ComplexField_class`
-    are of type :class:`ComplexNumber`::
-
-        sage: c = 1 + 2*I
-        sage: is_ComplexNumber(c)
-        False
-        sage: d = CC(1 + 2*I)
-        sage: is_ComplexNumber(d)
-        True
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_ComplexNumber is deprecated; "
-                       "use 'isinstance(..., ComplexNumber)' instead.")
-    return isinstance(x, ComplexNumber)
-
-
 cache = {}
 
 
diff --git a/src/sage/rings/finite_rings/integer_mod.pyx b/src/sage/rings/finite_rings/integer_mod.pyx
index cc1576f14a1..dcc40302f62 100644
--- a/src/sage/rings/finite_rings/integer_mod.pyx
+++ b/src/sage/rings/finite_rings/integer_mod.pyx
@@ -205,30 +205,6 @@ def IntegerMod(parent, value):
     return t(parent, value)
 
 
-def is_IntegerMod(x):
-    """
-    Return ``True`` if and only if x is an integer modulo
-    `n`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.finite_rings.integer_mod import is_IntegerMod
-        sage: is_IntegerMod(5)
-        doctest:warning...
-        DeprecationWarning: The function is_IntegerMod is deprecated;
-        use 'isinstance(..., IntegerMod_abstract)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        False
-        sage: is_IntegerMod(Mod(5,10))
-        True
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_IntegerMod is deprecated; "
-                       "use 'isinstance(..., IntegerMod_abstract)' instead.")
-    return isinstance(x, IntegerMod_abstract)
-
-
 cdef inline inverse_or_None(x):
     try:
         return ~x
diff --git a/src/sage/rings/fraction_field.py b/src/sage/rings/fraction_field.py
index 7ffbcae8f75..2e002b91918 100644
--- a/src/sage/rings/fraction_field.py
+++ b/src/sage/rings/fraction_field.py
@@ -142,29 +142,6 @@ def FractionField(R, names=None):
     return R.fraction_field()
 
 
-def is_FractionField(x) -> bool:
-    """
-    Test whether or not ``x`` inherits from :class:`FractionField_generic`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.fraction_field import is_FractionField
-        sage: is_FractionField(Frac(ZZ['x']))
-        doctest:warning...
-        DeprecationWarning: The function is_FractionField is deprecated;
-        use 'isinstance(..., FractionField_generic)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_FractionField(QQ)
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38128,
-                "The function is_FractionField is deprecated; "
-                "use 'isinstance(..., FractionField_generic)' instead.")
-    return isinstance(x, FractionField_generic)
-
-
 class FractionField_generic(ring.Field):
     """
     The fraction field of an integral domain.
diff --git a/src/sage/rings/fraction_field_element.pyx b/src/sage/rings/fraction_field_element.pyx
index d38499afb27..b04b7a2c7ab 100644
--- a/src/sage/rings/fraction_field_element.pyx
+++ b/src/sage/rings/fraction_field_element.pyx
@@ -29,32 +29,6 @@ import sage.misc.latex as latex
 import sage.misc.superseded
 
 
-def is_FractionFieldElement(x) -> bool:
-    """
-    Return whether or not ``x`` is a :class:`FractionFieldElement`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.fraction_field_element import is_FractionFieldElement
-        sage: R.<x> = ZZ[]
-        sage: is_FractionFieldElement(x/2)
-        doctest:warning...
-        DeprecationWarning: The function is_FractionFieldElement is deprecated;
-        use 'isinstance(..., FractionFieldElement)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        False
-        sage: is_FractionFieldElement(2/x)
-        True
-        sage: is_FractionFieldElement(1/3)
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_FractionFieldElement is deprecated; "
-                       "use 'isinstance(..., FractionFieldElement)' instead.")
-    return isinstance(x, FractionFieldElement)
-
-
 cdef class FractionFieldElement(FieldElement):
     """
     EXAMPLES::
diff --git a/src/sage/rings/ideal.py b/src/sage/rings/ideal.py
index 223c1884f9f..286e7e7572b 100644
--- a/src/sage/rings/ideal.py
+++ b/src/sage/rings/ideal.py
@@ -206,47 +206,6 @@ def Ideal(*args, **kwds):
     return I
 
 
-def is_Ideal(x):
-    r"""
-    Return ``True`` if object is an ideal of a ring.
-
-    EXAMPLES:
-
-    A simple example involving the ring of integers. Note
-    that Sage does not interpret rings objects themselves as ideals.
-    However, one can still explicitly construct these ideals::
-
-        sage: from sage.rings.ideal import is_Ideal
-        sage: R = ZZ
-        sage: is_Ideal(R)
-        doctest:warning...
-        DeprecationWarning: The function is_Ideal is deprecated; use 'isinstance(..., Ideal_generic)' instead.
-        See https://github.com/sagemath/sage/issues/38266 for details.
-        False
-        sage: 1*R; is_Ideal(1*R)
-        Principal ideal (1) of Integer Ring
-        True
-        sage: 0*R; is_Ideal(0*R)
-        Principal ideal (0) of Integer Ring
-        True
-
-    Sage recognizes ideals of polynomial rings as well::
-
-        sage: R = PolynomialRing(QQ, 'x'); x = R.gen()
-        sage: I = R.ideal(x^2 + 1); I
-        Principal ideal (x^2 + 1) of Univariate Polynomial Ring in x over Rational Field
-        sage: is_Ideal(I)
-        True
-        sage: is_Ideal((x^2 + 1)*R)
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38266,
-                "The function is_Ideal is deprecated; "
-                "use 'isinstance(..., Ideal_generic)' instead.")
-    return isinstance(x, Ideal_generic)
-
-
 class Ideal_generic(MonoidElement):
     """
     An ideal.
diff --git a/src/sage/rings/integer.pyx b/src/sage/rings/integer.pyx
index f173d7207fc..30e53aea1e9 100644
--- a/src/sage/rings/integer.pyx
+++ b/src/sage/rings/integer.pyx
@@ -321,33 +321,6 @@ mpz_init(PARI_PSEUDOPRIME_LIMIT)
 mpz_ui_pow_ui(PARI_PSEUDOPRIME_LIMIT, 2, 64)
 
 
-def is_Integer(x):
-    """
-    Return ``True`` if ``x`` is of the Sage :class:`Integer` type.
-
-    EXAMPLES::
-
-        sage: from sage.rings.integer import is_Integer
-        sage: is_Integer(2)
-        doctest:warning...
-        DeprecationWarning: The function is_Integer is deprecated;
-        use 'isinstance(..., Integer)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_Integer(2/1)
-        False
-        sage: is_Integer(int(2))
-        False
-        sage: is_Integer('5')
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_Integer is deprecated; "
-                       "use 'isinstance(..., Integer)' instead.")
-    return isinstance(x, Integer)
-
-
 cdef inline Integer as_Integer(x):
     if isinstance(x, Integer):
         return <Integer>x
diff --git a/src/sage/rings/integer_ring.pyx b/src/sage/rings/integer_ring.pyx
index 9b527515c75..fd975d8014a 100644
--- a/src/sage/rings/integer_ring.pyx
+++ b/src/sage/rings/integer_ring.pyx
@@ -86,33 +86,6 @@ cdef int number_of_integer_rings = 0
 _prev_discrete_gaussian_integer_sampler = (None, None)
 
 
-def is_IntegerRing(x):
-    r"""
-    Internal function: return ``True`` iff ``x`` is the ring `\ZZ` of integers.
-
-    TESTS::
-
-        sage: from sage.rings.integer_ring import is_IntegerRing
-        sage: is_IntegerRing(ZZ)
-        doctest:warning...
-        DeprecationWarning: The function is_IntegerRing is deprecated;
-        use 'isinstance(..., IntegerRing_class)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_IntegerRing(QQ)
-        False
-        sage: is_IntegerRing(parent(3))
-        True
-        sage: is_IntegerRing(parent(1/3))
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_IntegerRing is deprecated; "
-                       "use 'isinstance(..., IntegerRing_class)' instead.")
-    return isinstance(x, IntegerRing_class)
-
-
 cdef class IntegerRing_class(CommutativeRing):
     r"""
     The ring of integers.
diff --git a/src/sage/rings/laurent_series_ring.py b/src/sage/rings/laurent_series_ring.py
index 11cf1eee759..a1f9ee7aad0 100644
--- a/src/sage/rings/laurent_series_ring.py
+++ b/src/sage/rings/laurent_series_ring.py
@@ -57,34 +57,6 @@
 lazy_import('sage.rings.power_series_ring', 'PowerSeriesRing_generic')
 
 
-def is_LaurentSeriesRing(x):
-    """
-    Return ``True`` if this is a *univariate* Laurent series ring.
-
-    This is in keeping with the behavior of ``is_PolynomialRing``
-    versus ``is_MPolynomialRing``.
-
-    TESTS::
-
-        sage: from sage.rings.laurent_series_ring import is_LaurentSeriesRing
-        sage: K.<q> = LaurentSeriesRing(QQ)
-        sage: is_LaurentSeriesRing(K)
-        doctest:warning...
-        DeprecationWarning: The function is_LaurentSeriesRing is deprecated;
-        use 'isinstance(..., (LaurentSeriesRing, LazyLaurentSeriesRing))' instead.
-        See https://github.com/sagemath/sage/issues/38290 for details.
-        True
-        sage: L.<z> = LazyLaurentSeriesRing(QQ)
-        sage: is_LaurentSeriesRing(L)
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38290,
-                "The function is_LaurentSeriesRing is deprecated; "
-                "use 'isinstance(..., (LaurentSeriesRing, LazyLaurentSeriesRing))' instead.")
-    return isinstance(x, (LaurentSeriesRing, LazyLaurentSeriesRing))
-
-
 class LaurentSeriesRing(UniqueRepresentation, Parent):
     r"""
     Univariate Laurent Series Ring.
diff --git a/src/sage/rings/multi_power_series_ring.py b/src/sage/rings/multi_power_series_ring.py
index 97753556987..0de904059eb 100644
--- a/src/sage/rings/multi_power_series_ring.py
+++ b/src/sage/rings/multi_power_series_ring.py
@@ -225,46 +225,6 @@
                                             'LazyLaurentSeriesRing'))
 
 
-def is_MPowerSeriesRing(x):
-    """
-    Return ``True`` if input is a multivariate power series ring.
-
-    TESTS::
-
-        sage: from sage.rings.power_series_ring import is_PowerSeriesRing
-        sage: from sage.rings.multi_power_series_ring import is_MPowerSeriesRing
-        sage: M = PowerSeriesRing(ZZ, 4, 'v')
-        sage: is_PowerSeriesRing(M)
-        doctest:warning...
-        DeprecationWarning: The function is_PowerSeriesRing is deprecated;
-        use 'isinstance(..., (PowerSeriesRing_generic, LazyPowerSeriesRing) and ....ngens() == 1)' instead.
-        See https://github.com/sagemath/sage/issues/38290 for details.
-        False
-        sage: is_MPowerSeriesRing(M)
-        doctest:warning...
-        DeprecationWarning: The function is_MPowerSeriesRing is deprecated;
-        use 'isinstance(..., (MPowerSeriesRing_generic, LazyPowerSeriesRing))' instead.
-        See https://github.com/sagemath/sage/issues/38290 for details.
-        True
-        sage: T = PowerSeriesRing(RR, 'v')
-        sage: is_PowerSeriesRing(T)
-        True
-        sage: is_MPowerSeriesRing(T)
-        False
-        sage: L = LazyPowerSeriesRing(QQ, 'x')
-        sage: is_MPowerSeriesRing(L)
-        True
-        sage: L = LazyPowerSeriesRing(QQ, 'x, y')
-        sage: is_MPowerSeriesRing(L)
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38290,
-                "The function is_MPowerSeriesRing is deprecated; "
-                "use 'isinstance(..., (MPowerSeriesRing_generic, LazyPowerSeriesRing))' instead.")
-    return isinstance(x, (MPowerSeriesRing_generic, LazyPowerSeriesRing))
-
-
 class MPowerSeriesRing_generic(PowerSeriesRing_generic, Nonexact):
     r"""
     A multivariate power series ring.
diff --git a/src/sage/rings/multi_power_series_ring_element.py b/src/sage/rings/multi_power_series_ring_element.py
index 367e939977b..dca99100e44 100644
--- a/src/sage/rings/multi_power_series_ring_element.py
+++ b/src/sage/rings/multi_power_series_ring_element.py
@@ -167,40 +167,8 @@
 lazy_import('sage.rings.power_series_ring', 'PowerSeriesRing_generic')
 
 
-def is_MPowerSeries(f):
-    """
-    Return ``True`` if ``f`` is a multivariate power series.
-
-    TESTS::
-
-        sage: from sage.rings.power_series_ring_element import is_PowerSeries
-        sage: from sage.rings.multi_power_series_ring_element import is_MPowerSeries
-        sage: M = PowerSeriesRing(ZZ,4,'v')
-        sage: is_PowerSeries(M.random_element(10))
-        doctest:warning...
-        DeprecationWarning: The function is_PowerSeries is deprecated; use 'isinstance(..., PowerSeries)' instead.
-        See https://github.com/sagemath/sage/issues/38266 for details.
-        True
-        sage: is_MPowerSeries(M.random_element(10))
-        doctest:warning...
-        DeprecationWarning: The function is_MPowerSeries is deprecated; use 'isinstance(..., MPowerSeries)' instead.
-        See https://github.com/sagemath/sage/issues/38266 for details.
-        True
-        sage: T.<v> = PowerSeriesRing(RR)
-        sage: is_MPowerSeries(1 - v + v^2 +O(v^3))
-        False
-        sage: is_PowerSeries(1 - v + v^2 +O(v^3))
-        True
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38266,
-                "The function is_MPowerSeries is deprecated; "
-                "use 'isinstance(..., MPowerSeries)' instead.")
-    return isinstance(f, MPowerSeries)
-
-
 class MPowerSeries(PowerSeries):
-    ### methods from PowerSeries that we *don't* override:
+    # ## methods from PowerSeries that we *don't* override:
     #
     # __hash__ : works just fine
     #
diff --git a/src/sage/rings/power_series_ring.py b/src/sage/rings/power_series_ring.py
index 8c72090eff4..f0c99445d95 100644
--- a/src/sage/rings/power_series_ring.py
+++ b/src/sage/rings/power_series_ring.py
@@ -457,38 +457,6 @@ def _single_variate():
     pass
 
 
-def is_PowerSeriesRing(R):
-    """
-    Return ``True`` if this is a *univariate* power series ring.  This is in
-    keeping with the behavior of ``is_PolynomialRing``
-    versus ``is_MPolynomialRing``.
-
-    EXAMPLES::
-
-        sage: from sage.rings.power_series_ring import is_PowerSeriesRing
-        sage: is_PowerSeriesRing(10)
-        doctest:warning...
-        DeprecationWarning: The function is_PowerSeriesRing is deprecated;
-        use 'isinstance(..., (PowerSeriesRing_generic, LazyPowerSeriesRing) and ....ngens() == 1)' instead.
-        See https://github.com/sagemath/sage/issues/38290 for details.
-        False
-        sage: is_PowerSeriesRing(QQ[['x']])
-        True
-        sage: is_PowerSeriesRing(LazyPowerSeriesRing(QQ, 'x'))
-        True
-        sage: is_PowerSeriesRing(LazyPowerSeriesRing(QQ, 'x, y'))
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38290,
-                "The function is_PowerSeriesRing is deprecated; "
-                "use 'isinstance(..., (PowerSeriesRing_generic, LazyPowerSeriesRing) and ....ngens() == 1)' instead.")
-    if isinstance(R, (PowerSeriesRing_generic, LazyPowerSeriesRing)):
-        return R.ngens() == 1
-    else:
-        return False
-
-
 class PowerSeriesRing_generic(UniqueRepresentation, Parent, Nonexact):
     """
     A power series ring.
diff --git a/src/sage/rings/power_series_ring_element.pyx b/src/sage/rings/power_series_ring_element.pyx
index 03205e6838b..6489571a8a2 100644
--- a/src/sage/rings/power_series_ring_element.pyx
+++ b/src/sage/rings/power_series_ring_element.pyx
@@ -116,36 +116,6 @@ from sage.structure.element cimport AlgebraElement, RingElement
 from sage.structure.richcmp cimport richcmp
 
 
-def is_PowerSeries(x):
-    """
-    Return ``True`` if ``x`` is an instance of a univariate
-    or multivariate power series.
-
-    EXAMPLES::
-
-        sage: R.<x> = PowerSeriesRing(ZZ)
-        sage: from sage.rings.power_series_ring_element import is_PowerSeries
-        sage: is_PowerSeries(1 + x^2)
-        doctest:warning...
-        DeprecationWarning: The function is_PowerSeries is deprecated; use 'isinstance(..., PowerSeries)' instead.
-        See https://github.com/sagemath/sage/issues/38266 for details.
-        True
-        sage: is_PowerSeries(x - x)
-        True
-        sage: is_PowerSeries(0)
-        False
-        sage: var('x')                                                                  # needs sage.symbolic
-        x
-        sage: is_PowerSeries(1 + x^2)                                                   # needs sage.symbolic
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38266,
-                       "The function is_PowerSeries is deprecated; "
-                       "use 'isinstance(..., PowerSeries)' instead.")
-    return isinstance(x, PowerSeries)
-
-
 cdef class PowerSeries(AlgebraElement):
     """
     A power series. Base class of univariate and
diff --git a/src/sage/rings/qqbar.py b/src/sage/rings/qqbar.py
index 7c58d798690..0f180b13c0b 100644
--- a/src/sage/rings/qqbar.py
+++ b/src/sage/rings/qqbar.py
@@ -6763,56 +6763,6 @@ def scale(self):
         return self._value
 
 
-def is_AlgebraicReal(x):
-    r"""
-    Test if ``x`` is an instance of :class:`~AlgebraicReal`. For internal use.
-
-    EXAMPLES::
-
-        sage: from sage.rings.qqbar import is_AlgebraicReal
-        sage: is_AlgebraicReal(AA(sqrt(2)))                                             # needs sage.symbolic
-        doctest:warning...
-        DeprecationWarning: The function is_AlgebraicReal is deprecated;
-        use 'isinstance(..., AlgebraicReal)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_AlgebraicReal(QQbar(sqrt(2)))                                          # needs sage.symbolic
-        False
-        sage: is_AlgebraicReal("spam")
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38128,
-                "The function is_AlgebraicReal is deprecated; "
-                "use 'isinstance(..., AlgebraicReal)' instead.")
-    return isinstance(x, AlgebraicReal)
-
-
-def is_AlgebraicNumber(x):
-    r"""
-    Test if ``x`` is an instance of :class:`~AlgebraicNumber`. For internal use.
-
-    EXAMPLES::
-
-        sage: from sage.rings.qqbar import is_AlgebraicNumber
-        sage: is_AlgebraicNumber(AA(sqrt(2)))                                           # needs sage.symbolic
-        doctest:warning...
-        DeprecationWarning: The function is_AlgebraicNumber is deprecated;
-        use 'isinstance(..., AlgebraicNumber)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        False
-        sage: is_AlgebraicNumber(QQbar(sqrt(2)))                                        # needs sage.symbolic
-        True
-        sage: is_AlgebraicNumber("spam")
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38128,
-                "The function is_AlgebraicNumber is deprecated; "
-                "use 'isinstance(..., AlgebraicNumber)' instead.")
-    return isinstance(x, AlgebraicNumber)
-
-
 QQbarPoly = PolynomialRing(QQbar, 'x')
 AAPoly = PolynomialRing(AA, 'x')
 
diff --git a/src/sage/rings/quotient_ring.py b/src/sage/rings/quotient_ring.py
index 39856647a4f..e66179eaa25 100644
--- a/src/sage/rings/quotient_ring.py
+++ b/src/sage/rings/quotient_ring.py
@@ -336,42 +336,6 @@ def QuotientRing(R, I, names=None, **kwds):
     return QuotientRing_nc(R, I, names, **kwds)
 
 
-def is_QuotientRing(x):
-    """
-    Test whether or not ``x`` inherits from :class:`QuotientRing_nc`.
-
-    EXAMPLES::
-
-        sage: from sage.rings.quotient_ring import is_QuotientRing
-        sage: R.<x> = PolynomialRing(ZZ,'x')
-        sage: I = R.ideal([4 + 3*x + x^2, 1 + x^2])
-        sage: S = R.quotient_ring(I)
-        sage: is_QuotientRing(S)
-        doctest:warning...
-        DeprecationWarning: The function is_QuotientRing is deprecated;
-        use 'isinstance(..., QuotientRing_nc)' instead.
-        See https://github.com/sagemath/sage/issues/38266 for details.
-        True
-        sage: is_QuotientRing(R)
-        False
-
-    ::
-
-        sage: F.<x,y,z> = FreeAlgebra(QQ, implementation='letterplace')
-        sage: I = F * [x*y + y*z, x^2 + x*y - y*x - y^2] * F
-        sage: Q = F.quo(I)
-        sage: is_QuotientRing(Q)
-        True
-        sage: is_QuotientRing(F)
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38266,
-                "The function is_QuotientRing is deprecated; "
-                "use 'isinstance(..., QuotientRing_nc)' instead.")
-    return isinstance(x, QuotientRing_nc)
-
-
 _RingsQuotients = _Rings.Quotients()
 _CommutativeRingsQuotients = _CommRings.Quotients()
 
diff --git a/src/sage/rings/rational.pyx b/src/sage/rings/rational.pyx
index d92d33e7b7c..bd0ab4521dc 100644
--- a/src/sage/rings/rational.pyx
+++ b/src/sage/rings/rational.pyx
@@ -384,33 +384,6 @@ cpdef rational_power_parts(a, Rational b, factor_limit=10**5):
     return (c, d) if not b_negative else (c, ~d)
 
 
-def is_Rational(x):
-    """
-    Return ``True`` if ``x`` is of the Sage :class:`Rational` type.
-
-    EXAMPLES::
-
-        sage: from sage.rings.rational import is_Rational
-        sage: is_Rational(2)
-        doctest:warning...
-        DeprecationWarning: The function is_Rational is deprecated;
-        use 'isinstance(..., Rational)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        False
-        sage: is_Rational(2/1)
-        True
-        sage: is_Rational(int(2))
-        False
-        sage: is_Rational('5')
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_Rational is deprecated; "
-                       "use 'isinstance(..., Rational)' instead.")
-    return isinstance(x, Rational)
-
-
 cdef class Rational(sage.structure.element.FieldElement):
     """
     A rational number.
diff --git a/src/sage/rings/rational_field.py b/src/sage/rings/rational_field.py
index ac41c4643c9..9a8c41ca228 100644
--- a/src/sage/rings/rational_field.py
+++ b/src/sage/rings/rational_field.py
@@ -1671,29 +1671,6 @@ def valuation(self, p):
 Q = QQ
 
 
-def is_RationalField(x) -> bool:
-    """
-    Check to see if ``x`` is the rational field.
-
-    EXAMPLES::
-
-        sage: from sage.rings.rational_field import is_RationalField as is_RF
-        sage: is_RF(QQ)
-        doctest:warning...
-        DeprecationWarning: The function is_RationalField is deprecated;
-        use 'isinstance(..., RationalField)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_RF(ZZ)
-        False
-    """
-    from sage.misc.superseded import deprecation
-    deprecation(38128,
-                "The function is_RationalField is deprecated; "
-                "use 'isinstance(..., RationalField)' instead.")
-    return isinstance(x, RationalField)
-
-
 def frac(n, d):
     """
     Return the fraction ``n/d``.
diff --git a/src/sage/rings/real_double.pyx b/src/sage/rings/real_double.pyx
index 1b1f7404149..28cfeccaaff 100644
--- a/src/sage/rings/real_double.pyx
+++ b/src/sage/rings/real_double.pyx
@@ -2046,29 +2046,6 @@ def RealDoubleField():
     return _RDF
 
 
-def is_RealDoubleElement(x):
-    """
-    Check if ``x`` is an element of the real double field.
-
-    EXAMPLES::
-
-        sage: from sage.rings.real_double import is_RealDoubleElement
-        sage: is_RealDoubleElement(RDF(3))
-        doctest:warning...
-        DeprecationWarning: The function is_RealDoubleElement is deprecated;
-        use 'isinstance(..., RealDoubleElement)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_RealDoubleElement(RIF(3))
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_RealDoubleElement is deprecated; "
-                       "use 'isinstance(..., RealDoubleElement)' instead.")
-    return isinstance(x, RealDoubleElement)
-
-
 # ################ FAST CREATION CODE ######################
 #            Based on fast integer creation code
 #         There is nothing to see here, move along
diff --git a/src/sage/rings/real_mpfi.pyx b/src/sage/rings/real_mpfi.pyx
index 1964dc8e6af..ecfb649c554 100644
--- a/src/sage/rings/real_mpfi.pyx
+++ b/src/sage/rings/real_mpfi.pyx
@@ -5313,50 +5313,6 @@ def RealInterval(s, upper=None, int base=10, int pad=0, min_prec=53):
 RIF = RealIntervalField()
 
 
-def is_RealIntervalField(x):
-    """
-    Check if ``x`` is a :class:`RealIntervalField_class`.
-
-    EXAMPLES::
-
-        sage: sage.rings.real_mpfi.is_RealIntervalField(RIF)
-        doctest:warning...
-        DeprecationWarning: The function is_RealIntervalField is deprecated;
-        use 'isinstance(..., RealIntervalField_class)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: sage.rings.real_mpfi.is_RealIntervalField(RealIntervalField(200))
-        True
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_RealIntervalField is deprecated; "
-                       "use 'isinstance(..., RealIntervalField_class)' instead.")
-    return isinstance(x, RealIntervalField_class)
-
-
-def is_RealIntervalFieldElement(x):
-    """
-    Check if ``x`` is a :class:`RealIntervalFieldElement`.
-
-    EXAMPLES::
-
-        sage: sage.rings.real_mpfi.is_RealIntervalFieldElement(RIF(2.2))
-        doctest:warning...
-        DeprecationWarning: The function is_RealIntervalFieldElement is deprecated;
-        use 'isinstance(..., RealIntervalFieldElement)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: sage.rings.real_mpfi.is_RealIntervalFieldElement(RealIntervalField(200)(2.2))
-        True
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_RealIntervalFieldElement is deprecated; "
-                       "use 'isinstance(..., RealIntervalFieldElement)' instead.")
-    return isinstance(x, RealIntervalFieldElement)
-
-
 # pickle functions
 def __create__RealIntervalField_version0(prec, sci_not):
     """
diff --git a/src/sage/rings/real_mpfr.pyx b/src/sage/rings/real_mpfr.pyx
index 4b253b9e88e..a9aa7ad2fda 100644
--- a/src/sage/rings/real_mpfr.pyx
+++ b/src/sage/rings/real_mpfr.pyx
@@ -5954,34 +5954,6 @@ def create_RealNumber(s, int base=10, int pad=0, rnd='RNDN', int min_prec=53):
     return RealLiteral(R, s, base)
 
 
-def is_RealNumber(x):
-    """
-    Return ``True`` if ``x`` is of type :class:`RealNumber`, meaning that it
-    is an element of the MPFR real field with some precision.
-
-    EXAMPLES::
-
-        sage: from sage.rings.real_mpfr import is_RealNumber
-        sage: is_RealNumber(2.5)
-        doctest:warning...
-        DeprecationWarning: The function is_RealNumber is deprecated;
-        use 'isinstance(..., RealNumber)' instead.
-        See https://github.com/sagemath/sage/issues/38128 for details.
-        True
-        sage: is_RealNumber(float(2.3))
-        False
-        sage: is_RealNumber(RDF(2))
-        False
-        sage: is_RealNumber(pi)                                                         # needs sage.symbolic
-        False
-    """
-    from sage.misc.superseded import deprecation_cython
-    deprecation_cython(38128,
-                       "The function is_RealNumber is deprecated; "
-                       "use 'isinstance(..., RealNumber)' instead.")
-    return isinstance(x, RealNumber)
-
-
 def __create__RealField_version0(prec, sci_not, rnd):
     """
     Create a :class:`RealField_class` by calling :func:`RealField()`.