| Term | Definition |
| nyūyoku suru (入浴する) | to take a bath, to have a bath |
| nyūyō (入用) | need |
| ga nyūyō de aru (が入用である) | to want, to be needed |
| taipisuto nyūyō (タイピスト入用) | Wanted a typist |
| nyūyōji (乳幼児) | babies (and little children), infants |
| nyūzai (乳剤) | an emulsion |
| o (尾) | a tail, a brush, a trail |
| o (緒) | a cord, a string, a thong |
| oainikusama (お生憎様) | I'm sorry, but ... |
| oazuke o kuu (お預けを食う) | to be kept waiting |
| oba (伯母/叔母) | an aunt |
| obāsan (お婆さん) | a grandmother, a grandma, a granny; an old woman, an old lady |
| obake (お化け) | a boggy, a monster, a ghost, an apparition |
| obake ga deru (お化けが出る) | to be haunted |
| obakeyashiki (お化け屋敷) | a haunted house |
| obasan (小母さん) | an aunt, auntie; a lady, a woman |
| yoso no obasan (よその小母さん) | a (strange) lady |
| obekka (おべっか) | flattery [-> おべんちゃら] |
| obekka o tsukau (おべっかを使う) | to flatter [-> 言う] |
| obekka o iu (おべっかを言う) | to flatter [-> 使う] |
| obenchara (おべんちゃら) | flattery [-> おべっか] |
| obi (帯) | a belt, an obi, a sash, a girdle |
| obi o shimeru (帯を締める) | to tie a sash |
| obi o toku (帯を解く) | to undo a sash |
| obiji (帯地) | sash cloth |
| obiage (帯揚げ) | a sash bustle, an obi bustle |
| obijime (帯締め) | a sash band, an obi band |
| obidome (帯留め) | a sash clip, an obi clip |
| ōbī (オービー) | a graduate, an alumnus, an old boy |
| obieru (怯える/脅える) | to be frightened, to be scared |
| obikidasu (誘き出す) | to lure out of |
| obikiireru (誘き入れる) | to lure in(to) [-> 寄せる] |
| obikiyoseru (誘き寄せる) | to lure into [-> 入れる] |
| obiru (帯びる) | to wear, to carry; to be charged with; to have, to assume, to take on |
| kōyō o obite (公用を帯びて) | on official business |
| obitadashii (夥しい) | abundant, profuse, numerous |
| obitadashiku (夥しく) | abundantly, profusely, numerously |
| obiyakasu (脅かす) | to threaten, to frighten, to intimidate |
| oboe (覚え) | a memory; experience; favour |
| oboe ga yoi (覚えが良い) | to have a good memory, to be quick to learn |
| oboe ga warui (覚えが悪い) | to have a poor memory, to be slow to learn |
| oboe ga aru (覚えがある) | to remember |
| oboe ga nai (覚えがない) | to do not remember |
| ude ni oboe ga aru (腕に覚えがある) | to be confident of one's skill |
| oboegaki (覚書) | a memorandum, [Infml.] a memo, a note |
| oboeru (覚える) | to remember, to learn, to memorize, to learn by heart; to feel |
| oboreru (溺れる) | [水に] to be drowned; to indulge in, to give oneself up, to be addicted to |
| oborona (朧な) | dim, vague, hazy |
| oborogeni (朧気に) | dimly, faintly |
| oborozuki (朧月) | a hazy moon |
| oborozukiyo (朧月夜) | a misty moonlit night |
| oboshimeshi (思召) | your opinion; your fancy |
| oboshimeshi ni kanau (思召にかなう) | to suit a person's fancy |
| obotsukanai (覚束ない) | doubtful, uncertain; [There is] little hope [of] |
| oburāto (オブラート) | a medicinal wafer |
| obusaru (負ぶさる) | to ride on a person's back, to be carried on a person's back, to rely on |
| obutsu (汚物) | filth, dirt, dust, garbage, night soil |
| ocha (お茶) | tea; a tea/coffee break |
| ocha o nigosu (お茶を濁す) | to make (a) shift |
| ochi (落ち) | an omission, an oversight; [話の] the point, a punch line; the end |
| suru no ga ochi da (するのが落ちだ) | to be bound to result in |
| ochiau (落ち合う) | to meet (by appointment), to come across |
| ochiba (落葉) | a fallen leaf, a dead leaf |
| ochibo (落穂) | gleanings, fallen ears |
| ochibureru (落ちぶれる) | to fall low, to be reduced to poverty, [Infml.] to go to the dogs |
| ochido (落度) | a fault; a blame |
| ochido no nai (落度のない) | faultless, blameless |
| ochiiru (陥る) | to fall into, to yield to, to fall |
| ochikobore (落ちこぼれ) | a dropout |
| ochikomu (落ち込む) | to fall in, to fall into, to sink, to cave in; to be depressed |
| ochikubomu (落ち窪む) | to cave in, to sink |
| ochikubonda hō (落ち窪んだ頬) | hollow/sunken cheeks |
| ochime ni naru (落ち目になる) | One's fortune declines, One's star is on the wane |
| ochimusha (落武者) | a fugitive |
| ochiochi nemurenai (おちおち眠れない) | to cannot have a good sleep |
| ochiochi shite irarenai (おちおちしていられない) | to cannot be at rest |
| ochiru (落ちる) | to fall, to drop; to give way, to collapse; to be omitted; [日/月が] to set, to sink, [試験に] to fail, to fall into; [城が] to fall; [汚れ/しみが] to come off/out, [色が] to fade; [手形が] to be honoured |