fortnightly

This term is predominantly used in British English and other Commonwealth varieties. In North American English, it is far less common, where speakers typically prefer the phrase "every two weeks" or "biweekly."

Because "biweekly" is notoriously ambiguous—meaning both "twice a week" and "every two weeks"—"fortnightly" serves as a precise alternative that eliminates confusion by specifying a exact fourteen-day interval.