Definitions of perennial:

• noun:   a plant lasting for three seasons or more
• adjective:   lasting an indefinitely long time; suggesting self-renewal

  Example: "Perennial happiness"

• adjective:   recurring again and again

  Example: "Perennial efforts to stipulate the requirements"

• adjective:   lasting three seasons or more

  Example: "The common buttercup is a popular perennial plant"