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

• expostulation
• expostulatory
• exposure
• exposure meter
• exposure therapy
• expound
• expounder
• expounding
• express
• express emotion
• express feelings
• express joy
• express luxury liner
• express mirth
• express trust
• express-mail
• expressage
• expressed
• expressed almond oil
• expressible
• expression
• expressional
• expressionism
• expressionist
• expressionistic