Meaning

noun (botany) a plant that completes its entire life cycle within the space of a year

noun a reference book that is published regularly once every year

adjective completing its life cycle within a year

originFirst attested around 1382, borrowed from Late Latin annuālem, annuālis, related to Latin annālis, adjective form of annus (“year”). Used to categorize plants since 1710.

Etymology from Wiktionary, CC BY-SA 3.0