You use perennial to describe situations or states that keep occurring or which seem to exist all the time; used especially to describe problems or difficulties.
例句
...the perennial urban problems of drugs and homelessness...毒品和无家可归这两个一直困扰城市的问题There's a perennial shortage of teachers with science qualifications.有理科教学资格的老师一直都很短缺。
ADJ
（植物）多年生的
A perennial plant lives for several years and has flowers each year.
例句
...a perennial herb with greenish-yellow flowers.开绿黄色花的多年生香草