Apostrophes

In Plurals

Don't use apostrophes to form plurals of proper nouns, acronyms, and numerals. For example, the plural of FAQ is FAQs, not FAQ's.
Don't pluralize single letters, symbols, or mathematical signs by adding an apostrophe and an s.
- Incorrect: Salesforce replaces unrecognizable characters with @’s.
- Correct: Salesforce replaces unrecognizable characters with the at (@) sign.
To form the plural of a numeral, add s but no apostrophe: Type three 2s.
In abbreviations for measurements, don't add an s to indicate plurality. For example: 10 oz or 30 mm

In Possessives

To form the possessive case of singular nouns, including proper nouns ending in an s or z sound, use an apostrophe followed by an s.
To form the possessive of plural nouns, add an apostrophe only.
Don't use an apostrophe in these possessive pronouns: his, hers, its, ours, yours, theirs, and whose.

Salesforce.com Style Guide for Documentation and User Interface Text