An abbreviation is the shortened form of a word or a phrase. In general, use abbreviations only in tables, graphs, charts - places where space must be conserved. The following abbreviations, however, are acceptable in any form of writing:
Mr. Ms. Mrs. Dr. Jr. a.m. (A.M.)
Note: In the body of a letter or a report, spell out the names of states, countries, months, days, or units of measure. Also spell out the words Avenue, Street, Road, Company, and similar words when they are part of a proper name. Use words rather than signs or symbols (&,%,#,@).
A Closer Look
Avoid beginning a sentence with an abbreviation. Also, spell out abbreviations the first time they are used; then abbreviate, if appropriate.