| 一つ | ひとつ | one; for one thing; only; (not) even | n5 |
| 一番 | いちばん | number one; first; first place; best | n5 |
| 一覧 | いちらん | look; glance; sight; having a look at | n1 |
| 一方 | いっぽう | one (esp. of two); the other; one way; the other way | n4 |
| 一種 | いっしゅ | a kind; a sort; a variety; a species | n2 |
| 一緒 | いっしょ | (doing) together; one lump; one mixture; the same category | n5 |
| 一般 | いっぱん | general; universal; ordinary; average | n3 |
| 一部 | いちぶ | one part; one portion; one section; one copy (of a book) | n4 |
| 一度 | いちど | once; one time; on one occasion; temporarily | n5 |
| 一時 | ひととき | a (short) time; a while; moment; one time (in the past) | n3 |
| 一体 | いったい | (what) the heck; (why) in the world; (who) on earth; (where) the hell | n2 |
| 一層 | いっそう | even more; still more; all the more; more than ever | n2 |
| 一生 | いっしょう | whole life; a lifetime; all through life; (the only, the greatest, etc.) of one's life | n4 |
| 一言 | ひとこと | single word; a few words; brief comment | n2 |
| 一切 | いっさい | all; everything; entirety; the whole | n2 |
| 一 | いち | one; 1; best; first | n5 |
| もう一度 | もういちど | once more; again | |
| 唯一 | ゆいいつ | only; sole; unique | n2 |
| 一応 | いちおう | more or less; though not quite satisfactorily; after a fashion; pretty much | n3 |
| 一月 | いちがつ | January; first month of the lunar calendar | n5 |
| 一々 | いちいち | one-by-one; separately; every single; each and every | n2 |
| 一家 | いっか | a family; a household; a home; one's family | n1 |
| 一同 | いちどう | all present; all concerned; all of us | |
| 一向 | いっこう | completely; absolutely; totally; (not) at all | |
| 一生懸命 | いっしょうけんめい | very hard; with utmost effort; as hard as one can; with all one's might | n3 |
| 一致 | いっち | agreement; accord; correspondence; consistency | n2 |
| 一夜 | いちや | one night; all night; overnight; one evening | |
| 一人 | ひとり | one person; being alone; being by oneself; being single | n5 |
| 一定 | いってい | to fix; to settle; to standardize; to regularize | n2 |
| 十一月 | じゅういちがつ | November; eleventh month of the lunar calendar | n5 |
| 一見 | いっけん | look; glimpse; glance; apparently | n2 |
| 一行 | いちぎょう | (one) line; (one) row | |
| 統一 | とういつ | unity; consolidation; uniformity; unification | n2 |
| 一目 | ひとめ | glance; look; glimpse; complete view | n1 |
| 万一 | まんいち | (unlikely event of) emergency; the worst(-case scenario); 10000 to 1; (if) by some chance | |
| 一刻 | いっこく | a moment; a minute; an instant; stubborn | n1 |
| 一杯 | いっぱい | one cup (of); one glass (of); one bowl (of); cupful | n5 |
| 一旦 | いったん | once; for a short time; briefly; temporarily | n2 |
| 一瞬 | いっしゅん | instant; moment; for an instant | n2 |
| 一室 | いっしつ | one room | |
| 一般的 | いっぱんてき | general; popular; common; typical | n3 |
| 一足 | いっそく | a pair (of shoes or socks) | |
| 一流 | いちりゅう | first-class; first-rate; top-flight; top-ranking | n3 |
| 同一 | どういつ | identical; same; one and the same; equal | n2 |
| 一寸 | いっすん | one sun (approx. 3 cm); little bit (of time, distance, etc.) | |
| 一緒に | いっしょに | together (with); at the same time; in one lump; in the same category | |
| 一座 | いちざ | the whole company; the party; all those present; everyone in attendance | |
| 一帯 | いったい | whole area; whole region; stretch (of land); tract | n2 |
| 一文 | いちもん | tiny amount of money; a penny; a cent; a farthing | |
| 一間 | いっけん | one ken (approx. 1.8 m) | n2 |
| 一段 | いちだん | even more; still more; much more; further | n3 |
| 一向に | いっこうに | completely; absolutely; totally; (not) at all | |
| 一片 | いっぺん | a piece; a scrap; a fragment; a bit | n1 |
| 一筋 | ひとすじ | one line; one stretch (e.g. of road); one strand (e.g. of hair); one beam (e.g. of light) | n1 |
| 何一つ | なにひとつ | (not) one | |
| 一団 | いちだん | body; group; party; gang | n3 |
| 一斉 | いっせい | simultaneous; all at once | |
| 一隅 | いちぐう | corner; nook | |
| 一様 | いちよう | uniform; equal; even; the same | n3 |
| 一息 | ひといき | one breath; time of one breath; pause; break | n1 |
| 一節 | いっせつ | one passage; one paragraph; one stanza; one verse | |
| 一大 | いちだい | one large ...; a great ... | |
| 一等 | いっとう | first class; first rank; first grade; first place | |
| 一部分 | いちぶぶん | one part; one portion; one section | n3 |
| 一気に | いっきに | in one go; in one gulp; in one breath; without stopping | n2 |
| 一端 | いったん | one end; an end; part; fragment | n1 |
| 一貫 | いっかん | consistency; coherence; integration; one kan (approx. 3.75 kg) | n1 |
| 一事 | いちじ | one thing | n3 |
| 一族 | いちぞく | family; relatives; dependents; household | n1 |
| 一角 | いっかく | corner; section; point; part | n2 |
| 一句 | いっく | phrase (verse, line); one haiku-poem | n2 |
| 一昨日 | おととい | day before yesterday | n3 |
| 一変 | いっぺん | complete change; about-face | n2 |
| 一口 | ひとくち | mouthful; morsel; bite; gulp | n2 |
| 一身 | いっしん | oneself; one's body | n1 |
| 一昨年 | おととし | year before last | n2 |
| 一声 | いっせい | voice; cry; shout | |
| 一所 | いっしょ | one place; the same place; one person; together | n5 |
| 一心 | いっしん | one mind; wholeheartedness; one's whole heart | n1 |
| 一般に | いっぱんに | generally; in general; widely; commonly | |
| 日本一 | にほんいち | Japan's best; number one in Japan | |
| 一心に | いっしんに | wholeheartedly; single-mindedly; fervently; intently | |
| 一群 | いちぐん | group; flock; crowd; herd | |
| 一服 | いっぷく | a puff; a smoke; a cup of tea; (short) rest | |
| 一途 | いちず | single-minded; intent; determined; wholehearted | n1 |
| 一味 | いちみ | clan; partisans; conspirators; gang | |
| 一ぱい | いっぱい | one cup (of); one glass (of); one bowl (of); cupful | n5 |
| 一語 | いちご | one word | n5 |
| 一滴 | いってき | one drop (of fluid) | |
| 一挙 | いっきょ | one effort; one action | |
| 一瞥 | いちべつ | a glance; a look; a glimpse | |
| 一派 | いっぱ | one school; one sect; one denomination; one party | |
| 今一つ | いまひとつ | one more; another (one); (not) quite; (not) entirely | n2 |
| 一念 | いちねん | determined purpose; an incredibly short span of time (i.e. the time occupied by a single thought); a single repetition of a prayer (esp. in Jodo-shu) | |
| 一撃 | いちげき | one blow; one hit; one stroke; summiting on the first attempt (oft. without prior knowledge about the route; in climbing) | |
| 精一杯 | せいいっぱい | the best one can do; one's best effort; with all one's might; to the best of one's ability | n2 |
| 一直線 | いっちょくせん | straight line | n1 |
| 第一歩 | だいいっぽ | first step | n2 |
| 一代 | いちだい | generation; lifetime; age | |
| 一遍 | いっぺん | once; one time; exclusively; only | n2 |