Correct Use of Apostrophes

Most apostrophe errors involve adding an apostrophe where it is not needed, rather than leaving one out where it is required.  When in doubt, do not add an apostrophe.

Most of the time, apostrophes are used to indicate possession or to show that a letter has been left out in a contraction.  If you're not doing either of those things, don't add an apostrophe.  If you are adding an "s" to make a noun plural, do not add an apostrophe.  Ask for three carrots, not three carrot’s.