opus

n (pl opera / 5CpErE; `BpErE/) 1 musical composition numbered as one of a composer's works (work1 5b) (usu in order of publication) 编号的音乐作品（通常以出版的先後为序）: Beethoven's opus 112贝多芬第112号作品. 2 (fml 文) work of art, esp on a large scale 艺术作品; （尤指）巨著, 大作.

optic, optical, optical art, optical illusion, optically, optician, optics, optimal, optimism, optimist, optimistic, optimistically, optimization, optimize, optimum, option, optional, optometrist, opulence, opulent, or, or else, or rather, or so, oracle, oracular, oral, orally, orang-utan, orange, orange squash, orange-blossom, orange-coloured, orangeade, orate, oration, orator, oratorical, oratorio, oratory,