'Per annum' definitions:

Definition of 'per annum'

(from WordNet)
adverb
By the year; every year (usually with reference to a sum of money paid or received); "he earned $100,000 per annum"; "we issue six volumes per annum" [syn: per annum, p.a., per year, each year, annually]

Definition of 'Per annum'

From: GCIDE
  • Per \Per\, prep. [L. Cf. Far, For-, Pardon, and cf. Par, prep.] Through; by means of; through the agency of; by; for; for each; as, per annum; per capita, by heads, or according to individuals; per curiam, by the court; per se, by itself, of itself. Per is also sometimes used with English words. [1913 Webster]
  • Per annum, by the year; in each successive year; annually.
  • per cent, Per centum, percent, by the hundred; in the hundred; a proportion multiplied by one hundred; -- used esp. of proportions of ingredients, rate or amount of interest, and the like; most commonly used in the shortened form per cent; as, 5 is ten per cent of 50. It is commonly symbolized with the per cent sign, "%".
  • Per diem, by the day. [For other phrases from the Latin, see Quotations, Phrases, etc., from Foreign Languages, in the Supplement.] [1913 Webster]