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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.

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:

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


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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See Also

As, since, because and for
A lot of, lots of, plenty of, a great deal of
Below and under
Above and over
Both and both of
As if and as though
Fairly, quite, pretty and rather
Finally, at last, in the end and at the end
No and none


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