1pe·ren·ni·al 
/pəˈrɛnijəl/ adjective
/pəˈrɛnijəl/ adjective 1 of a plant : living for several years or for many years : having a life cycle that is more than two years long
▪ a perennial plant ▪ This variety of oregano is perennial. — compare 1annual, 1biennial 2 a : existing or continuing in the same way for a long time
▪ Hot dogs are a perennial favorite at barbecues. [=people always like to eat hot dogs at barbecues]
b : happening again and again
▪ Flooding is a perennial problem for people living by the river.
▪ a perennial plant ▪ This variety of oregano is perennial. — compare 1annual, 1biennial
▪ Hot dogs are a perennial favorite at barbecues. [=people always like to eat hot dogs at barbecues]
b : happening again and again
▪ Flooding is a perennial problem for people living by the river.
— pe·ren·ni·al·ly adverb
▪ a perennially popular restaurant
▪ a perennially popular restaurant
