1 sth that is added
ADJ. useful, valuable, welcome, worthy | important, major, notable, significant | latest, new, recent
VERB + ADDITION make We have made several additions to the collection recently.
PREP. ~ to the latest addition to the family (= a new baby)
2 process of adding numbers/amounts
ADJ. simple He worked it out through simple addition.
VERB + ADDITION do She can do addition, but she hasn't learned subtraction yet.