n.
Variant: or ortho-
Function: combining form
Etymology: Greek, from orthos straight, right, true; akin to Sanskrit ū rdhva high, upright
1 : straight : upright : vertical < ortho grade>
2 : perpendicular < ortho rhombic>
3 : correct : corrective < orth odontia>
4 a : hydrated or hydroxylated to the highest degree < ortho phosphoric acid> b : involving substitution at or characterized by or having the relationship of two neighboring positions in the benzene ring < ortho- xylene>