addition (n.)

late 14c., "to join or unite (something to something else)," from Latin addere "add to, join, attach, place upon," literal and figurative, from ad "to" (see ad-) + -dere, combining form meaning "to put, place," from dare "to give" (from PIE root *do- "to give").

The intransitive meaning "to do sums, do addition" also is from late 14c. Related: Added; adding. To add up is from 1754; in the figurative meaning "make sense," by 1942. Adding machine "machine to cast up large sums" is from 1822.

1640s, "added, supplementary," from addition + -al (1). Related: Additionally.

1690s, "tending to be added," from Late Latin additivus "added, annexed," past-participle adjective from Latin addere "add to, join, attach" (see addition). Alternative addititious "additive, additional" (1748) is from Latin additicius "additional."