Not true. You may use an apostrophe with a plural acronym. Using Apostrophes in Awkward Plurals The first thing to make clear before we start this lesson is that apostrophes are not normally used for forming plurals. (This is covered more in the lesson apostrophe errors with plurals.) Using an apostrophe to form a plural is usually a grammatical howler. However, sometimes, a plural is so awkward, it is permissible to use an apostrophe to assist your readers. For example: There are two a's in accommodation.