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).
a combining form used in the name of that acid in a given series of acids that contains the most water (orthoboric acid).Compare meta-, pyro-.
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)).
correct or rightorthodontics; orthodox; orthography; orthoptics
(often in italics)denoting an organic compound containing a benzene ring with substituents attached to adjacent carbon atoms (the 1,2- positions)orthodinitrobenzene Abbreviation: o- Compare oarsman Compare oarsman
denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acidorthophosphoric acid See meta- (def. 6)
denoting a diatomic substance in which the spins of the two atoms are parallelorthohydrogen See para- 1 (def. 8)
before vowels orth-, word-forming element meaning "straight, upright, rectangular, regular; true, correct, proper," now mostly in scientific and technical compounds, from Greek ortho-, stem of orthos "straight, true, correct, regular," from PIE *eredh- "high" (cf. Sanskrit urdhvah "high, lofty, steep," Latin arduus "high, steep," Old Irish ard "high").