per·en·ni·al 
(pə-rĕnē-əl)
(pə-rĕnē-əl)adj.
1.
a. Lasting an indefinitely long time; enduring: an author's perennial popularity among children.
b. Appearing again and again or year after year; recurrent: a perennial contender for the championship. See Synonyms at continual.
2. Botany Living three or more years.
3. Lasting or active throughout the year: a perennial stream.
n.
1. Botany A perennial plant.
2. Something that recurs or seems to recur on a yearly or continual basis: "that hardy perennial, the budget deficit" (David S. Broder).
[Latin perennis (per-, throughout; see PER- + annus, year; see at- in the Appendix of Indo-European roots) + -AL1.]
per·enni·al·ly adv.