Odont-
Greek; tooth
-odynia
Greek; condition of pain
Oen-/oeno-
Greek; pain
-oid
Latin from Greek; resembling
Olig-
Greek; few, little
-oma
Greek; tumor
Onmat-
Greek; eye
Omni-
Latin; all
Onych-/onycho-
Greek; nail
-onym
Greek; name
-ophthalm
Greek; eye
Opt-/opto-
Greek; vision, eye
Or-
Latin; mouth
Oro-
Greek; mountain
Ortho-
Greek; right, straight
-osis
Greek; (medical) condition
Osteo-
Greek; bone
-oso
Italian; full of
Oss-
Latin; bone
Ot-
Greek; ear
-ous
Latin; full of
Oxy-
Greek, sharp, quick