Definition:Summand/Also known as

Summand: Also known as
The word addend appears to mean the same thing as summand, such that the two words may be used interchangeably.

The word term is frequently seen for summand, but term also has other meanings.

If it is important to avoid ambiguity then it is recommended that summand is used.

The term augend can sometimes be seen for (specifically) the first of a pair of summands, so in the context of $a + b = c$:
 * $a$ is the augend
 * $b$ is the addend
 * $c$ is the sum.