isotonic /ī-sō-tonˈik/

1. Having the same tone, tension or osmotic pressure
2. (of muscular contraction) shortening the muscle fibres and moving a joint
3. (of an energy drink) containing salts and minerals of the same concentration as in the body

• one another
• one-armed bandit
• on earth
• one by one
• one day
• one-day
• on edge
• one-dimensional
• one-er
• one-eyed
• one fell swoop
• one flesh
• onefold
• one for his nob
• one for the road
• one-handed
• one-horse
• one-horse race
• one-horse races
• one-idea'd
• one in a million
• one in a thousand
• one in the eye
• oneiric
• oneirocritic