annum

Annum is a Latin noun meaning "a year" that has been adopted into English as a formal, technical term. It is most often seen in phrases such as per annum, meaning "for each year" or "over a year." It is used to express annual rates or amounts, especially in finance, law, and academia. Examples include interest rates, salaries, budgets, and penalties stated per annum.

Usage notes: The phrase per annum is common in Commonwealth English and formal writing; in American English, per year or annually is more common in everyday use, though per annum persists in statutory language and international finance. Grammatically, annum is used in the singular in English; its Latin plural "anni" or "annums" is not usually used in ordinary English.

Etymology: derived from Latin annus "year", with per annum meaning "through the year". The term appears in older legal and financial documents and remains in contemporary formal contexts, often abbreviated as p.a.