Technical Writing A–Z: A Commonsense Guide to Engineering Reports and Theses (U.S. Edition)
1 Abbreviated Terms
■ Abbreviations (shortened forms of words), acronyms (words formed from the initial letters of other words), and initialisms (groups of letters, which are pronounced separately, taken from the initial letters of other words) usually require an explanation. The general rule is to spell out the full name when the item is first mentioned, followed by the abbreviation in parentheses—for example: Onboard Oxygen Generating Systems (OBOGS)—and thereafter to use the abbreviation. You can underline the letters that make up the abbreviation if you wish—for example: ANOVA (Analysis of variance).
■ When the abbreviated term is itself widely understood (e.g., AIDS, DNA, NATO), it is not necessary to give the full name in the text; however, it could still be included in the list of abbreviations for completeness (DNA can also mean Distributed interNet Application).
■ It is common practice not to use periods with such abbreviations (Internet Protocol, for example, would be written as IP rather than I.P.). Plurals are formed by adding an s without an apostrophe.