Use the apostrophe before an "s" to indicate the possessive (i.e. something that is of or belonging to something else – the graduating class of Memorial).

• Memorial’s graduating class

If something is descriptive rather than possessive, it does not take an apostrophe (the guide for students, the college for teachers, the point guard for the Sea-Hawks).

In cases where the noun ends in an "s", use a single apostrophe after the "s".

• The Faculty of Business’ student teams
• Professor Bridget Jenkins’ research

Note that the "s" followed by an apostrophe reads awkwardly, so it might be better to rewrite the sentence.

• Student teams in the Faculty of Business
• Research by Professor Bridget Jenkins

In cases where the possessive is plural, use a single apostrophe after the "s" or rewrite the sentence.

• The students’ grades will be posted.
• The senators’ votes were counted at the end of the meeting.

or

• Grades will be posted.
• At the end of the senate meeting, the results of the vote were counted.

Use an apostrophe with plurals of lower case letters.

• Mind your p’s and q’s. Dot the i’s and cross the t’s.

Capital letters and numbers have no apostrophe before plural-s.

• She got straight As. We teach the three Rs.
• The 1960s was a decade of rapid growth for York University.

(See the Numbers and Dates & Times sections.)

Do not use an apostrophe with the possessive pronoun "its".

• The program is in its third year.

Use an apostrophe with the contraction meaning "it is".

• It’s a difficult course.

(See the Possessives section.)