D defs.my
Entry 2 senses Webster, 1913

Ortho-

/(ôr"thō̇-)/ · Or·tho- · IPA /oɹ.θə-/
01 pref. A combining form signifying straight, right, upright, correct, regular; as, orthodromy, orthodiagonal, orthodox, orthographic.
  1. 1.
    A combining form signifying straight, right, upright, correct, regular; as, orthodromy, orthodiagonal, orthodox, orthographic.
  2. 2.
    A combining form (also used adjectively)(Chem.)