RhymeZone: ortho definitions

Definitions of ortho:

noun: (countable, chemistry) An isomer of a benzene derivative having two substituents adjacent on the ring.
noun: (countable, astronomy) A certain type of flat eyepiece.
noun: (countable, photography, dated) An orthochromatic plate.
noun: (countable, imaging) An orthophoto.
noun: (uncountable, medicine) Orthopedics.

(Definitions from Wiktionary)