Find the number of "leaves" in an expression tree:

These are the leaves in the expression:

Find leaf count measures of the sizes of successive integrals:

Make Simplify pick expressions with minimum LeafCount:

Find leaf counts in combinator expressions [more info]:

LeafCount by default includes the head and all elements inside it:

For expressions with atomic heads, this corresponds to the number of vertices in TreeForm[expr]:

LeafCount[expr,HeadsFalse] typically gives the number of leaves in TreeForm[expr]:

LeafCount counts elements in rational and complex numbers just as in FullForm:

LeafCount counts the head and values of an Association:

These are the five leaves in the expression:

Reversing the keys and values gives a different result:

LeafCount treats atomic objects, such as SparseArray objects, as single expression leaves:

SparseArray objects have a complicated FullForm:

But they are atomic:

For most expressions, LeafCount equals the count matching Blank[] at level {-1}:

LeafCount counts Rational and Complex numbers using their FullForm:

Count treats Rational and Complex as atoms:

LeafCount is based on the FullForm of expressions:

LeafCount by default includes leaves in heads:

The head f is considered a leaf, even though it is not a leaf in a tree visualization of the expression:

Use the setting HeadsFalse to only count the leaves of the tree visualization:

Unlike TreeForm, LeafCount takes into consideration the structure of expression heads:

This shows the expression tree whose leaves are counted by LeafCount: