lg is the common mathematical symbol for the

logarithm to the

base of 2.

The unit of lg x, in

number theory, is commonly known as a

bit. As such, it can commonly be used in

computer science, for example, when analyzing the height of a

binary tree, using lg x is helpful since there are two branches per

node. Using

O notation, lg x can be used instead of log x, since they differ only by a

constant.

It can also be written as log_2 x, read as the

logarithm to the

base 2 of x.