In Arithmetic:
A number to be subtracted from another number is known as Subtrahend E.g. 20  5 In the above arithmetic expression, 5 is a Subtrahend
Consider the following figure illustrating Subtrahend:
In Algebra:
An algebraic number to be subtracted from another algebraic number is known as Subtrahend E.g. 2a  2b In the above algebraic expression, 2b is a Subtrahend
Consider the following figure illustrating Subtrahend:

