Definition:Leading Term

Definition
Let $P = a \circ b$ be an expression.

The term $a$ is known as the leading term of $P$.

Also known as
$a$ is also known, particularly in, as the antecedent of $P$.

However, as this has a specific usage in the field of logic, it is preferred that the term not be used in this context.

Also see

 * Definition:Following Term