Periods and question marks
Use a period to end a statement and a question mark to end a direct question. An exclamation mark signals strong feeling or emphasis and is best used selectively.
Commas separate and clarify
Commas separate items in a series, set off introductory elements and mark some nonessential information. A comma alone should not join two complete sentences.
Apostrophes show possession or contraction
Apostrophes form contractions and possessives. They do not usually make a noun plural. Distinguish “its” from “it's” when editing.
Quotation marks and colons
Quotation marks identify quoted material and certain titles, depending on the style guide. A colon can introduce an explanation, list or example after a complete clause.
Frequently asked questions
Can a comma splice two full sentences?
In standard formal writing, use a period, semicolon or coordinating conjunction instead of a comma alone.
Does a plural noun need an apostrophe?
Usually not. Apostrophes mark possession or contractions, not ordinary plurals.