APS House Style :: Punctuation

Apostrophes

When to Use an Apostrophe

To indicate possession (e.g., "the author's," "colleagues'," and "the cell's").

To pluralize single letters, both capital and lowercase, and single-digit numbers.

When Not to Use an Apostrophe

To pluralize an abbreviation, acronym, or year (in those cases, use a lowercase "s"), e.g., EEGs.