6. Technical Abbreviations, Acronyms, and
Units of Measurement
While you usually do not have to add any punctuation to abbreviations and acronyms, a few exceptions are made.
- Use periods or other punctuation marks in abbreviations or acronyms when it is standard form.
in. for inch
I/O for input/output
3-D for three-dimensional
- Add an "s" and no apostrophe to form the plural of abbreviations or acronyms that contain no periods.
- Add an apostrophe and "s" to form the plural of abbreviations or acronyms that use internal periods.