orris-root

n sweet-smelling root of certain types of iris plant, dried and used in perfumes and medicines 鸢尾根（用作香料或药材）.

original, original sin, originality, originally, originate, originator, oriole, ormolu, ornament, ornamental, ornamentation, ornate, ornately, ornateness, ornithological, ornithologist, ornithology, orotund, orphan, orphanage, orth(o)-, orthodontic, orthodontics, orthodontist, orthodox, orthodoxy, orthographic (also orthographical), orthographically, orthography, orthopaedic (also orthopedic), orthopaedics (also orthopedics), orthopaedist (also orthopedist), ortolan, oryx, OS, Oscar, oscillate, oscillation, oscillator, oscillograph,