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ortho-(word root) straight
Examples of words with the root ortho-: orthodontia
[1875–80; independent use of ortho-]
1. a combining form meaning “straight,” “upright,” “right,” “correct”: orthodontics; orthopedic.
2.Also, esp. before a vowel, orth-.
a. a combining form used in the name of the most hydrated acid in a given series: orthoboric acid. Compare meta- (def. 2a), pyro- (def. 2a).
b. a combining form used in the names of benzene derivatives in which the substituting group occupies the ortho position in the benzene ring.
[< Greek, comb. form of orthós straight, upright, correct]