diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index e7376e4..0438afd 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -74,6 +74,7 @@
 
     @abstractmethod
     def next(self):
+        'Return the next item from the iterator. When exhausted, raise StopIteration'
         raise StopIteration
 
     def __iter__(self):
@@ -194,6 +195,7 @@
         return self._from_iterable(value for value in other if value in self)
 
     def isdisjoint(self, other):
+        'Return True if two sets have a null intersection.'
         for value in other:
             if value in self:
                 return False
@@ -259,6 +261,16 @@
 
 
 class MutableSet(Set):
+    """A mutable set is a finite, iterable container.
+
+    This class provides concrete generic implementations of all
+    methods except for __contains__, __iter__, __len__,
+    add(), and discard().
+
+    To override the comparisons (presumably for speed, as the
+    semantics are fixed), all you have to do is redefine __le__ and
+    then the other operations will automatically follow suit.
+    """
 
     @abstractmethod
     def add(self, value):
@@ -333,11 +345,20 @@
 
 class Mapping(Sized, Iterable, Container):
 
+    """A Mapping is a generic container for associating key/value
+    pairs.
+
+    This class provides concrete generic implementations of all
+    methods except for __getitem__, __iter__, and __len__.
+
+    """
+
     @abstractmethod
     def __getitem__(self, key):
         raise KeyError
 
     def get(self, key, default=None):
+        'D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.'
         try:
             return self[key]
         except KeyError:
@@ -352,23 +373,29 @@
             return True
 
     def iterkeys(self):
+        'D.iterkeys() -> an iterator over the keys of D'
         return iter(self)
 
     def itervalues(self):
+        'D.itervalues() -> an iterator over the values of D'
         for key in self:
             yield self[key]
 
     def iteritems(self):
+        'D.iteritems() -> an iterator over the (key, value) items of D'
         for key in self:
             yield (key, self[key])
 
     def keys(self):
+        "D.keys() -> list of D's keys"
         return list(self)
 
     def items(self):
+        "D.items() -> list of D's (key, value) pairs, as 2-tuples"
         return [(key, self[key]) for key in self]
 
     def values(self):
+        "D.values() -> list of D's values"
         return [self[key] for key in self]
 
     # Mappings are not hashable by default, but subclasses can change this
@@ -443,6 +470,15 @@
 
 class MutableMapping(Mapping):
 
+    """A MutableMapping is a generic container for associating
+    key/value pairs.
+
+    This class provides concrete generic implementations of all
+    methods except for __getitem__, __setitem__, __delitem__,
+    __iter__, and __len__.
+
+    """
+
     @abstractmethod
     def __setitem__(self, key, value):
         raise KeyError
@@ -454,6 +490,9 @@
     __marker = object()
 
     def pop(self, key, default=__marker):
+        '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
+          If key is not found, d is returned if given, otherwise KeyError is raised.
+        '''
         try:
             value = self[key]
         except KeyError:
@@ -465,6 +504,9 @@
             return value
 
     def popitem(self):
+        '''D.popitem() -> (k, v), remove and return some (key, value) pair
+           as a 2-tuple; but raise KeyError if D is empty.
+        '''
         try:
             key = next(iter(self))
         except StopIteration:
@@ -474,6 +516,7 @@
         return key, value
 
     def clear(self):
+        'D.clear() -> None.  Remove all items from D.'
         try:
             while True:
                 self.popitem()
@@ -481,6 +524,11 @@
             pass
 
     def update(*args, **kwds):
+        ''' D.update([E, ]**F) -> None.  Update D from mapping/iterable E and F.
+            If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
+            If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
+            In either case, this is followed by: for k, v in F.items(): D[k] = v
+        '''
         if len(args) > 2:
             raise TypeError("update() takes at most 2 positional "
                             "arguments ({} given)".format(len(args)))
@@ -502,6 +550,7 @@
             self[key] = value
 
     def setdefault(self, key, default=None):
+        'D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D'
         try:
             return self[key]
         except KeyError:
@@ -546,12 +595,16 @@
             yield self[i]
 
     def index(self, value):
+        '''S.index(value) -> integer -- return first index of value.
+           Raises ValueError if the value is not present.
+        '''
         for i, v in enumerate(self):
             if v == value:
                 return i
         raise ValueError
 
     def count(self, value):
+        'S.count(value) -> integer -- return number of occurrences of value'
         return sum(1 for v in self if v == value)
 
 Sequence.register(tuple)
@@ -562,6 +615,13 @@
 
 class MutableSequence(Sequence):
 
+    """All the operations on a read-only sequence.
+
+    Concrete subclasses must provide __new__ or __init__,
+    __getitem__, __setitem__, __delitem__, __len__, and insert().
+
+    """
+
     @abstractmethod
     def __setitem__(self, index, value):
         raise IndexError
@@ -572,26 +632,36 @@
 
     @abstractmethod
     def insert(self, index, value):
+        'S.insert(index, object) -- insert object before index'
         raise IndexError
 
     def append(self, value):
+        'S.append(object) -- append object to the end of the sequence'
         self.insert(len(self), value)
 
     def reverse(self):
+        'S.reverse() -- reverse *IN PLACE*'
         n = len(self)
         for i in range(n//2):
             self[i], self[n-i-1] = self[n-i-1], self[i]
 
     def extend(self, values):
+        'S.extend(iterable) -- extend sequence by appending elements from the iterable'
         for v in values:
             self.append(v)
 
     def pop(self, index=-1):
+        '''S.pop([index]) -> item -- remove and return item at index (default last).
+           Raise IndexError if list is empty or index is out of range.
+        '''
         v = self[index]
         del self[index]
         return v
 
     def remove(self, value):
+        '''S.remove(value) -- remove first occurrence of value.
+           Raise ValueError if the value is not present.
+        '''
         del self[self.index(value)]
 
     def __iadd__(self, values):