dyad /dīˈad/

1. A pair of units treated as one
2. A bivalent atom, radical, or element (chem)

• two-sidedness
• twosome
• twosomes
• two-speed gear
• two-start thread
• two-step
• two-steps
• two-storey
• two-storeyed
• two strings to one's bow
• twostroke
• twostrokes
• two ticks
• two-time
• two-timed
• two-timer
• two-timers
• two-times
• two-timing
• two-tone
• 'twould
• two-up
• two-ups
• two-up, two-down
• two-way