ad—adoptō, āre, āvī, ātus, to take to one’s self by choice, adopt.
opulentus [ops], adj., rich, wealthy.
opus, eris, n., work, labor; need, necessity; opus est with abl., there is need of; māgnō opere, greatly; tantō opere, so greatly.
ōrāculum, ī [ōrō], n., an oracle; a prophecy.
ōrātiō, ōnis [ōrō], f., a speech, oration, discourse.
ōrātor, ōris [ōrō], m., speaker, pleader, ambassador.
orbis, is, m., ring, circle, orbit; orbis terrārum (or orbis alone), the world.
orbus, adj., bereft (of parents or children), parentless, childless. As noun, orbus, ī, m., an orphan.
ōrdinō, āre, āvī, ātus [ōrdō], to set in order, arrange, adjust, regulate.
ōrdior, īrī, ōrsus sum, to begin.