biennial /bī-enˈi-əl or -enˈyəl/

1. Lasting two years
2. Happening or appearing once in two years

1. A plant that flowers and fruits only in its second year, then dies
2. An event taking place or being celebrated every two years

biennˈially adverb

• tree diagrams
• tree farm
• tree farms
• tree fern
• tree ferns
• tree frog
• tree frogs
• tree heath
• tree hopper
• tree hoppers
• tree house
• tree houses
• tree-hugger
• tree-huggers
• tree-hugging
• treeing
• tree kangaroo
• tree kangaroos
• treeless
• treelessness
• treelessnesses
• treelike
• tree lilies
• tree lily
• tree line