[приставка, первая часть сложных слов, греческий язык, буквально] "прямой" орфо-, орто-, прямо-, право- Например: orthography — орфография, правописание orthodontist [медицина] — ортодонт orthograde [зоология] — прямоходящий
or ortho- combining form Etymology: Greek, from orthos straight, right, true; akin to Sanskrit ūrdhva high, upright 1. straight; upright; vertical Example: orthograde 2. perpendicular Example: orthorhombic 3. correct; corrective Example: orthodontia 4. a. hydrated or hydroxylated to the highest degree Example: orthophosphoric acid b. involving substitution at or characterized by or having the relationship of two neighboring positions in the benzene ring Example: ortho-xylene