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Meaning of ortho

or•tho

Pronunciation: (ôr'thō), [key]
— adj. Chem.
  1. pertaining to or occupying two adjacent positions in the benzene ring. Cf.,.

ortho-

Pronunciation: [key]
  1. a combining form occurring in loanwords from Greek, where it meant “straight,” “upright,” “right,” “correct” (orthodox) and on this model used in the formation of compound words (orthopedic).
    1. a combining form used in the name of that acid in a given series of acids that contains the most water (orthoboric acid). Cf.meta-, pyro-.
    2. a combining form used in the names of the salts of these acids: if the acid ends in -ic, the corresponding salt ends in -ate (orthoboric acid (H3BO3) and potassium orthoborate (K3BO3)); if the acid ends in -ous, the corresponding salt ends in -ite (orthoantimonous acid (H3SbO3) and potassium orthoantimonite (K3SbO3)).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.