Definition of ortho- in English:


Pronunciation: /ˈɔːθəʊ/

combining form

  • 1Straight; rectangular; upright: orthodontics
  • 1.1Right; correct: orthoepy
  • 2 Chemistry Denoting substitution at two adjacent carbon atoms in a benzene ring, e.g. in 1,2 positions: orthodichlorobenzene Compare with meta- and para-1.
  • 3 Chemistry Denoting a compound from which a meta-compound is formed by dehydration: orthophosphoric acid


from Greek orthos 'straight, right'.

More definitions of ortho-

Definition of ortho- in:

Get more from Oxford Dictionaries

Subscribe to remove adverts and access premium resources

Word of the day maelstrom
Pronunciation: ˈmeɪlstrəm
a powerful whirlpool in the sea

Shop for an Oxford dictionary

Find the perfect Oxford dictionary for you in our online shop.