diff --git a/pandas/_libs/groupby.pyx b/pandas/_libs/groupby.pyx
index 53e66c4b8723d..d5d706650bb34 100644
--- a/pandas/_libs/groupby.pyx
+++ b/pandas/_libs/groupby.pyx
@@ -9,11 +9,9 @@ cimport numpy as cnp
 from numpy cimport (ndarray,
                     int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
                     uint32_t, uint64_t, float32_t, float64_t, complex64_t, complex128_t)
+from numpy.math cimport NAN
 cnp.import_array()
 
-cdef extern from "numpy/npy_math.h":
-    float64_t NAN "NPY_NAN"
-
 from pandas._libs.util cimport numeric, get_nat
 
 from pandas._libs.algos cimport (swap, TiebreakEnumType, TIEBREAK_AVERAGE,
diff --git a/pandas/_libs/hashtable.pyx b/pandas/_libs/hashtable.pyx
index e80f134290a7e..c3dcbb942d7fe 100644
--- a/pandas/_libs/hashtable.pyx
+++ b/pandas/_libs/hashtable.pyx
@@ -8,10 +8,9 @@ from libc.stdlib cimport malloc, free
 import numpy as np
 cimport numpy as cnp
 from numpy cimport ndarray, uint8_t, uint32_t, float64_t
+from numpy.math cimport NAN
 cnp.import_array()
 
-cdef extern from "numpy/npy_math.h":
-    float64_t NAN "NPY_NAN"
 
 from pandas._libs.khash cimport (
     khiter_t,
@@ -54,7 +53,7 @@ from pandas._libs.khash cimport (
 )
 
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 
 from pandas._libs.missing cimport checknull
 
diff --git a/pandas/_libs/index.pyx b/pandas/_libs/index.pyx
index 245c554570ce4..b4dcdaa10d0ef 100644
--- a/pandas/_libs/index.pyx
+++ b/pandas/_libs/index.pyx
@@ -19,11 +19,10 @@ from numpy cimport (
 cnp.import_array()
 
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 
-from pandas._libs.tslibs import Period, Timedelta
 from pandas._libs.tslibs.nattype cimport c_NaT as NaT
-from pandas._libs.tslibs.base cimport ABCTimestamp
+from pandas._libs.tslibs.base cimport ABCTimestamp, ABCTimedelta, ABCPeriod
 
 from pandas._libs.hashtable cimport HashTable
 
@@ -470,7 +469,7 @@ cdef class TimedeltaEngine(DatetimeEngine):
         return 'm8[ns]'
 
     cdef int64_t _unbox_scalar(self, scalar) except? -1:
-        if not (isinstance(scalar, Timedelta) or scalar is NaT):
+        if not (isinstance(scalar, ABCTimedelta) or scalar is NaT):
             raise TypeError(scalar)
         return scalar.value
 
@@ -480,7 +479,7 @@ cdef class PeriodEngine(Int64Engine):
     cdef int64_t _unbox_scalar(self, scalar) except? -1:
         if scalar is NaT:
             return scalar.value
-        if isinstance(scalar, Period):
+        if isinstance(scalar, ABCPeriod):
             # NB: we assume that we have the correct freq here.
             return scalar.ordinal
         raise TypeError(scalar)
diff --git a/pandas/_libs/internals.pyx b/pandas/_libs/internals.pyx
index 1e53b789aa05c..1aa95e92b73d1 100644
--- a/pandas/_libs/internals.pyx
+++ b/pandas/_libs/internals.pyx
@@ -1,5 +1,6 @@
-import cython
 from collections import defaultdict
+
+import cython
 from cython import Py_ssize_t
 
 from cpython.slice cimport PySlice_GetIndicesEx
diff --git a/pandas/_libs/interval.pyx b/pandas/_libs/interval.pyx
index 657a2798f7267..3850b24fdf519 100644
--- a/pandas/_libs/interval.pyx
+++ b/pandas/_libs/interval.pyx
@@ -33,7 +33,7 @@ from numpy cimport (
 cnp.import_array()
 
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 
 from pandas._libs.hashtable cimport Int64Vector
 from pandas._libs.tslibs.util cimport (
@@ -42,8 +42,7 @@ from pandas._libs.tslibs.util cimport (
     is_timedelta64_object,
 )
 
-from pandas._libs.tslibs import Timestamp
-from pandas._libs.tslibs.timedeltas import Timedelta
+from pandas._libs.tslibs.base cimport ABCTimestamp, ABCTimedelta
 from pandas._libs.tslibs.timezones cimport tz_compare
 
 
@@ -329,7 +328,7 @@ cdef class Interval(IntervalMixin):
             raise ValueError(f"invalid option for 'closed': {closed}")
         if not left <= right:
             raise ValueError("left side of interval must be <= right side")
-        if (isinstance(left, Timestamp) and
+        if (isinstance(left, ABCTimestamp) and
                 not tz_compare(left.tzinfo, right.tzinfo)):
             # GH 18538
             raise ValueError("left and right must have the same time zone, got "
@@ -341,7 +340,7 @@ cdef class Interval(IntervalMixin):
     def _validate_endpoint(self, endpoint):
         # GH 23013
         if not (is_integer_object(endpoint) or is_float_object(endpoint) or
-                isinstance(endpoint, (Timestamp, Timedelta))):
+                isinstance(endpoint, (ABCTimestamp, ABCTimedelta))):
             raise ValueError("Only numeric, Timestamp and Timedelta endpoints "
                              "are allowed when constructing an Interval.")
 
@@ -371,7 +370,7 @@ cdef class Interval(IntervalMixin):
         right = self.right
 
         # TODO: need more general formatting methodology here
-        if isinstance(left, Timestamp) and isinstance(right, Timestamp):
+        if isinstance(left, ABCTimestamp) and isinstance(right, ABCTimestamp):
             left = left._short_repr
             right = right._short_repr
 
diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 658f7fb202531..bd623a39010f6 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -1,6 +1,5 @@
 from collections import abc
 from decimal import Decimal
-
 import warnings
 
 import cython
@@ -63,7 +62,7 @@ cdef extern from "numpy/arrayobject.h":
 cdef extern from "src/parse_helper.h":
     int floatify(object, float64_t *result, int *maybe_int) except -1
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 from pandas._libs.util cimport is_nan, UINT64_MAX, INT64_MAX, INT64_MIN
 
 from pandas._libs.tslib import array_to_datetime
diff --git a/pandas/_libs/missing.pyx b/pandas/_libs/missing.pyx
index 6bca5e370ac89..6d4d1e95fe8c3 100644
--- a/pandas/_libs/missing.pyx
+++ b/pandas/_libs/missing.pyx
@@ -8,7 +8,7 @@ cimport numpy as cnp
 from numpy cimport ndarray, int64_t, uint8_t, float64_t
 cnp.import_array()
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 
 
 from pandas._libs.tslibs.np_datetime cimport get_datetime64_value, get_timedelta64_value
diff --git a/pandas/_libs/parsers.pyx b/pandas/_libs/parsers.pyx
index 9bb5e10348e47..461419239c730 100644
--- a/pandas/_libs/parsers.pyx
+++ b/pandas/_libs/parsers.pyx
@@ -34,7 +34,7 @@ cimport numpy as cnp
 from numpy cimport ndarray, uint8_t, uint64_t, int64_t, float64_t
 cnp.import_array()
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 from pandas._libs.util cimport UINT64_MAX, INT64_MAX, INT64_MIN
 import pandas._libs.lib as lib
 
diff --git a/pandas/_libs/reduction.pyx b/pandas/_libs/reduction.pyx
index a7b2d5d5491d5..0988cd7ff0dde 100644
--- a/pandas/_libs/reduction.pyx
+++ b/pandas/_libs/reduction.pyx
@@ -14,7 +14,7 @@ from numpy cimport (ndarray,
                     flatiter)
 cnp.import_array()
 
-cimport pandas._libs.util as util
+from pandas._libs cimport util
 from pandas._libs.lib import maybe_convert_objects, is_scalar
 
 
@@ -603,7 +603,7 @@ cdef class BlockSlider:
             arr.shape[1] = 0
 
 
-def compute_reduction(arr: np.ndarray, f, axis: int = 0, dummy=None, labels=None):
+def compute_reduction(arr: ndarray, f, axis: int = 0, dummy=None, labels=None):
     """
 
     Parameters
diff --git a/pandas/_libs/reshape.pyx b/pandas/_libs/reshape.pyx
index aed5e1d612088..da4dd00027395 100644
--- a/pandas/_libs/reshape.pyx
+++ b/pandas/_libs/reshape.pyx
@@ -15,11 +15,12 @@ from numpy cimport (
     uint64_t,
 )
 
-cimport numpy as cnp
 import numpy as np
-from pandas._libs.lib cimport c_is_list_like
+cimport numpy as cnp
 cnp.import_array()
 
+from pandas._libs.lib cimport c_is_list_like
+
 ctypedef fused reshape_t:
     uint8_t
     uint16_t
diff --git a/pandas/_libs/testing.pyx b/pandas/_libs/testing.pyx
index 0460a69f366c4..9d3959d0a070a 100644
--- a/pandas/_libs/testing.pyx
+++ b/pandas/_libs/testing.pyx
@@ -1,4 +1,8 @@
 import numpy as np
+from numpy cimport import_array
+import_array()
+
+from pandas._libs.util cimport is_array
 
 from pandas.core.dtypes.missing import isna, array_equivalent
 from pandas.core.dtypes.common import is_dtype_equal
@@ -116,8 +120,8 @@ cpdef assert_almost_equal(a, b,
         assert a == b, f"{a} != {b}"
         return True
 
-    a_is_ndarray = isinstance(a, np.ndarray)
-    b_is_ndarray = isinstance(b, np.ndarray)
+    a_is_ndarray = is_array(a)
+    b_is_ndarray = is_array(b)
 
     if obj is None:
         if a_is_ndarray or b_is_ndarray:
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 3a9639a700953..e8d602502d6d0 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -19,7 +19,7 @@ cnp.import_array()
 
 
 from pandas._libs.tslibs cimport util
-from pandas._libs.tslibs.util cimport is_integer_object
+from pandas._libs.tslibs.util cimport is_integer_object, is_datetime64_object
 
 from pandas._libs.tslibs.base cimport ABCTick, ABCTimestamp, is_tick_object
 
@@ -161,7 +161,7 @@ def apply_wraps(func):
         elif isinstance(other, (timedelta, BaseOffset)):
             # timedelta path
             return func(self, other)
-        elif isinstance(other, (np.datetime64, datetime, date)):
+        elif isinstance(other, (datetime, date)) or is_datetime64_object(other):
             other = Timestamp(other)
         else:
             # This will end up returning NotImplemented back in __add__
diff --git a/pandas/_libs/tslibs/strptime.pyx b/pandas/_libs/tslibs/strptime.pyx
index a209f71dd0676..884578df3e00b 100644
--- a/pandas/_libs/tslibs/strptime.pyx
+++ b/pandas/_libs/tslibs/strptime.pyx
@@ -5,6 +5,8 @@ import locale
 import calendar
 import re
 
+from cpython cimport datetime
+
 from _thread import allocate_lock as _thread_allocate_lock
 
 import pytz
@@ -12,8 +14,6 @@ import pytz
 import numpy as np
 from numpy cimport int64_t
 
-cimport cpython.datetime as datetime
-
 from pandas._libs.tslibs.np_datetime cimport (
     check_dts_bounds, dtstruct_to_dt64, npy_datetimestruct)
 
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index ab8f9b6c30eb1..0982cf8e5da33 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -25,7 +25,7 @@ from pandas._libs.tslibs.util cimport (
     is_timedelta64_object, is_array,
 )
 
-from pandas._libs.tslibs.base cimport ABCTimestamp, is_tick_object
+from pandas._libs.tslibs.base cimport ABCTimedelta, ABCTimestamp, is_tick_object
 
 from pandas._libs.tslibs cimport ccalendar
 
@@ -355,10 +355,10 @@ cdef class _Timestamp(ABCTimestamp):
 
         elif PyDelta_Check(other):
             # logic copied from delta_to_nanoseconds to prevent circular import
-            if hasattr(other, 'delta'):
+            if isinstance(other, ABCTimedelta):
                 # pd.Timedelta
                 nanos = other.value
-            elif PyDelta_Check(other):
+            else:
                 nanos = (other.days * 24 * 60 * 60 * 1000000 +
                          other.seconds * 1000000 +
                          other.microseconds) * 1000