1. Occurring every second year
   - biennial 
2. Occurring or payable twice each year
   - semiannual, biannual, half-yearly

1. Every two years
   - biennially 
2. Twice a year
   - semiannually

See also: periodic, periodical

• chiropractic
• chiropractor
• Chiroptera
• chiropteran
• chirp
• chirper
• chirpily
• chirpiness
• chirpy
• chirr
• chirrup
• chirurgeon
• chirurgical
• chisel
• chisel in
• chisel steel
• chisel-like
• chiseled
• chiseler
• chiselled
• chiseller
• Chisholm Trail
• Chishona
• Chisinau
• Chislev