IPA: /əˈpɒstrəfi/
KK: /əˈpɑstrəfi/
A punctuation mark used to show that letters have been left out of a word, to indicate possession, or to form plurals of letters and numbers.
In the word "it's", the apostrophe shows that the letters 'i' and 's' have been omitted.
Apostrophe → It is formed from "apo-" (meaning away from) and "strophe" (from Greek "strophē", meaning a turn or a bending). The word originally referred to a turning away, particularly in rhetoric when addressing someone not present.
Think of 'turning away' ('apo-') from the main subject to address someone else ('strophe') — that's why an apostrophe is used to indicate possession or omission.