ortho-
/ˈɔːθəʊ/combiningForm
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
Origin
From Greek orthos 'straight, right'.