Annum is a year, in phrases about rates and pay. Per annum, thirty thousand per annum, five per cent per annum.
It appears only in the Latin phrase per annum and never alone, which is why it looks odd on its own. Per annum matters in advertisements for credit, since a monthly rate quoted without it hides the real cost.
1nounannumA year, in phrases about rates and pay.
“The job pays thirty thousand pounds per annum, plus a bonus.”
annum is a year.
Latin annus means a year, and the phrase per annum means by the year.
Latin
per annum — yearly
English, today
annum
Built from
From Latin per annum (“yearly”), from annus (“year”).
Etymology from Wiktionary, CC BY-SA