Wikipedia:Manual of Style/Abbreviations

This guideline covers the use of abbreviations—including acronyms and initialisms, contractions, and other shortenings—in the English Wikipedia.

Maintaining a consistent abbreviation style allows Wikipedia to be read, written, edited, and navigated more easily by readers and editors. The style should always be consistent within a page. If a guideline conflicts with the correct usage of a proper name, ignore it. Abbreviations in quotations from written sources should always be written exactly as in the source, unless it is a Wikipedia-made translation.

Always consider whether it is better to write a word or phrase out in full, thus avoiding potential confusion for those not familiar with its abbreviation. Remember that Wikipedia does not have the same space constraints as paper.