U.S. or US? Use of Periods in US and USA

The abbreviation for United States may be written with or without periods between the letters—U.S. or US—depending on the style you follow. Although it has conventionally been written with internal periods, style manuals now differ in their recommendations.

Thus, both styles are acceptable—US and U.S., with and without periods. General advice is to omit the periods in formal styles, except if you specifically follow AP or APA style or are writing for a government publication. If in doubt, respect the style followed by your client, organization, university, or publication. In news copy, omit the periods in headlines.

Abbreviation vs. full form

In academic and other formal writing, prefer to use the full form (United States) in running text, restricting the use of the abbreviation (US or U.S.) to captions, headings, headlines, tables, and charts.

Also prefer the full form, United States, over the abbreviated U.S. or US when you need to use the name as a noun (the economy of the United States), using the abbreviation only adjectivally (the US dollar).

Periods in USA?

Don’t use periods in USA. Style authorities agree that the abbreviation USA is written without internal periods.

Other abbreviated names

Periods are generally omitted in UK and EU, except in AP style, which recommends U.K. and U.N. but EU (and UK and UN in headlines). Acronyms (which are abbreviations pronounced as words) such as NASA, NATO, UNICEF, and UNESCO also don’t contain periods.

Quick Quiz

Which is/are correct?
Choose from these answers
All done!
Which is preferred?
Choose from these answers
All done!
Which is preferred in formal styles?
Choose from these answers
All done!