bimonthly

Bimonthly is a term with two competing meanings. It can describe something that occurs every two months, or something that occurs twice per month. The ambiguity arises from the prefix bi- meaning two and from inconsistent historical usage. Because month lengths vary, calendars can also complicate the interpretation.

In practice, many editors and style guides discourage using bimonthly without clarification. The safer, explicit phrases are "every two months" and "twice a month" or "on a bi-monthly schedule" followed by a concrete example. Some sources also use "semi-monthly" to mean twice per month, though this too can be ambiguous in practice, as some consider it to indicate a mid-month and end-of-month payment or release.

Etymology traces bimonthly to bi- (two) and mensis (month). The same ambiguity affects related terms such as biweekly, leading to confusion about whether events occur every two weeks or twice per week. Because precision matters in scheduling, many organizations prefer unambiguous language such as "every other month" or "twice per month" and specify exact dates when possible.

See also: biweekly, semi-monthly, every two months, twice a month.