Apostrophes (‘) are used for three reasons: possession (boy’s bike), contraction (don’t) or omission (Rock ‘n’ Roll). Today I’ll cover contractions and omissions.

For both contractions and omissions, the apostrophe replaces the missing letter.

Contraction examples would be:
   you’re for you are, where it replaces the a in are
   it’s for it is where the apostrophe replaces the i in is

Omission examples would be:
   gone fishin’ where the apostrophe replaces the g
   pot o’ gold where the apostrophe replaces the f
   rock ’n’ roll where the apostrophe replaces the a and d in and

In a date when part of the year is left out, the apostrophe needs to indicate the missing year. In the 80s would mean the temperature; In the ‘80s would mean the decade.