In general, spell out acronyms on first mention, and include the acronym in parentheses immediately following the expanded form. On subsequent mention in the same topic or article, you can use the acronym without spelling it out. Exceptions to this guideline are indicated in the table. When you spell out the acronym, follow the capitalization given in the Expanded form column of the table unless noted otherwise.

Microsoft style

1-gigabyte (GB) hard disk

information stored in random access memory (RAM)

If the first mention appears in a title or heading, use your best judgment to determine how much information to include. For example, if space is limited, use the acronym without spelling it out. If the acronym and its spelled-out form are both important keywords, include them both in a title or heading to optimize their exposure to search engines. In the first sentence after the title or heading, provide the expanded form followed by the acronym in parentheses.

Choose an indefinite article (a or an) based on the acronym’s pronunciation.

Microsoft style

a RAM drive

an SDK

an OEM

If an acronym represents a singular noun, add a lowercase s to make it plural. Do not add an apostrophe before the s. If an acronym already represents a plural noun, do not add an s.

Microsoft style

three OEMs

frequently asked questions (FAQ)

Not Microsoft style

three OEM’s

Microsoft Foundation Classes (MFCs)