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Abbreviations are shortened forms of words or phrases. In strict analysis, they are distinct from contractions, which use an apostrophe, and initialisms. An initialism is formed from some or all of the initial letters of words in a phrase. Below, references to abbreviations should be taken to include acronyms, and the term acronym to apply also to initialisms.
Write out both the full version and the abbreviation at first occurrence
When an abbreviation will be used in an article, first introduce it using the full expression:
an early local area network (LAN) developed by Digital Equipment Corporation (DEC) ... DEC's later LAN products were ...
- Integers from zero to nine are spelled out in words. Integers greater than nine expressible in one or two words may be expressed either in numerals or in words. Other numbers are given in numerals or in forms such as 21 million.
- In general, use a comma in numbers with five or more digits to the left of the decimal point. Numbers with four digits are at the editor's discretion: 12,345, but either 1,000 or 1000.
- Write out "million" and "billion" on the first use. After that, unspaced "M" can be used for millions and "bn" for billions: 70M and 25bn.
- Write 3%, three percent, or three per cent, but not 3 % (with a space) or three %. "Percent" is American usage, and "per cent" is British usage.
- Scientific notation (e.g., 5.8×107 kg) is preferred in scientific contexts.