Definition of “apostrophe” - Learner’s Dictionary

apostrophe

noun [ C ] uk us /əˈpɒstrəfi/
ABSENT

B2 a mark (') used to show that letters or numbers are absent:

I'm (= I am) hungry.
I graduated in '09 (= 2009).
BELONGING

B2 a punctuation mark (') used before the letter 's' to show that something belongs to someone or something:

I drove my brother's car.

(Definition of “apostrophe” from the Cambridge Learner's Dictionary © Cambridge University Press)