oration

n. 演说,致辞,叙述法

optional, optometrist, opulence, opulent, opus, or, or else, or rather, or so, oracle, oracular, oral, orally, orang-utan, orange, orange squash, orange-blossom, orange-coloured, orangeade, orate, orator, oratorical, oratorio, oratory, orb, orbit, orbital, orch, orchard, orchestra, orchestra pit, orchestra stalls (US orchestra), orchestral, orchestrate, orchestration, orchid, ordain, ordeal, order, order-book,