- Biennial: Happening every to years
- Bilingual: Speaking two languages
- Duplex: A house that has two separate units
- Monochrome: One color
- Monopoly: Control by one person or one company
- Quadrangle: A figure with four sides and angles
- Triathlan: An athletic contest usually involving swimming, running, and biking
- Trilogy: A group of three plays or books with a common theme
- Unicorn: A horse like animal with one horn
- Unify: To make one