English Grammar

Acronyms and initialisms

An acronym is an abbreviation that is formed by combining the first letter or letters of several words. Acronyms are pronounced as words and are written without periods.

• Radio detecting and ranging (radar)
• Common Business-Oriented Language (COBOL)
• Self-contained underwater breathing apparatus (scuba)

Write acronyms in capital letters without periods. The only exceptions are those acronyms that have become accepted as common nouns, which are written in lowercase letters.

Examples: laser, radar, scuba

An initialism is an abbreviation that is formed by combining the initial letter of each word in a multiword term. Initialisms are pronounced as separate letters.

Examples are:

• End of month (e.o.m.)
• Cash on delivery (c.o.d.)

Initialisms may be written either uppercase or lowercase. Periods are not generally used when they are upper case.

Examples:

• EDP or e.d.p.
• EOM or e.o.m.
• OD or o.d.

Form the plural of an acronym or initialism by adding an s. Do not use an apostrophe.

Examples are: MIRVs, CRTs

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