verb

1. To join or unite (e.g. one thing to another, or as several particulars) so as to increase the number, augment the quantity or enlarge the magnitude, or so as to form into one aggregate.

2. To sum up; to put together mentally.

   “to add numbers”

3. To combine elements of (something) into one quantity.

   “to add a column of numbers”

Synonyms: coalesce, join, unite, bestow, give, annex, augment, increase