adj. & n.
--adj.
1. lasting through a year or several years.
2 (of a plant) lasting several years (cf. ANNUAL).
3 lasting a long time or for ever.
4 (of a stream) flowing through all seasons of the year.
--n. a perennial plant (a herbaceous perennial).
Derivatives:
perenniality n. perennially adv.
Etymology: L perennis (as PER-, annus year)