The use of the apostrophe ( ‘ ) is so misunderstood. It has 2 major uses. (1) To denote the possessive by adding (’s) eg. the doctor’s office, Christine’s book and (2) To denote a contraction or missing letters eg. don’t (do not), she’ll (she will).It should not be used in words that are simply plurals such as 1980s (not 1980’s), and the dos and don’ts (not dos and don’t’s).