大分
だいぶ
daibu
= considerably; greatly; quite a lot
大分（だいぶ）is an adverb that signals a notable degree of change or quantity — closer to “considerably” or “quite a lot” than a mild “a little.” Its most memorable quirk for learners is that the same kanji spell the name of a Japanese prefecture, but that place name is read おおいた, not だいぶ — a distinction that trips up even intermediate students.
だいぶ expresses that something has reached a significant, noticeable degree, but stops short of extremes like 非常に (hijō ni, “extremely”) or 完全に (kanzen ni, “completely”). It is most naturally paired with verbs or adjectives describing gradual change — recovery from illness, progress on a project, or the passage of time. Because it implies “more than expected” or “more than before,” it often carries a mildly surprised or relieved tone. In casual speech だいぶ is by far the more common form; in formal writing or careful speech you may also encounter だいぶん (with the final ん), which carries the same meaning but sounds slightly more deliberate.
The most common mistake learners make is confusing だいぶ (daibu, considerably) with the prefecture 大分 (Oita). When you see 大分 in a sentence without a の or geographic context after it, read it as だいぶ. A second pitfall is treating だいぶ as interchangeable with ちょっと (a little) — they sit at opposite ends of the degree scale. Finally, だいぶ pairs naturally with change-of-state verbs (良くなった, 減った, 進んだ) rather than static descriptions; pairing it with the past-tense form of an adjective to imply something became noticeably more so is especially idiomatic.
大 means “big” or “large,” and 分 means “part” or “portion.” Together the characters suggest “a large portion” of something, which maps onto the sense of “to a considerable degree.” The same 分 appears in 気分 (kibun, mood) and 自分 (jibun, oneself), where it carries the idea of a share or measure. Critically, the same two kanji form 大分県 — the prefecture in Kyushu — but there they are read おおいた, a completely unrelated reading rooted in the region’s historical name. Remembering that だいぶ uses the on-yomi (Sino-Japanese reading) while おおいた uses the kun-yomi (native Japanese reading) is a reliable way to keep them apart.
Everyday use
薬を飲んで、熱はだいぶ下がりました。
Kusuri wo nonde, netsu wa daibu sagarimashita.
I took some medicine and my fever has gone down considerably.
Casual / Social Media
あの映画、だいぶ前に観たけど、ラストシーンだけ覚えてる。
Ano eiga, daibu mae ni mita kedo, rasuto shīn dake oboeteru.
I watched that movie quite a long time ago, but I only remember the final scene.
Formal / Cultural context
ご説明にだいぶお時間をいただきまして、ありがとうございました。
Go-setsumei ni daibu ojikan wo itadakimashite, arigatō gozaimashita.
Thank you for taking a considerable amount of your time to explain this to us.
だいぶ sits in the middle of Japanese’s rich spectrum of degree adverbs. ちょっと and 少し mark the low end (a little), while だいぶ and かなり occupy the substantial-but-not-extreme middle ground, and 非常に or とても push toward the upper range. Among the mid-range peers, ずいぶん tends to carry a stronger sense of personal surprise (“wow, that’s really a lot”), whereas けっこう often softens a potentially blunt statement (“it’s quite good, actually”). だいぶ is the most neutral of the group — it simply marks a notable quantity or degree without strong emotional coloring.
The variant form だいぶん (with a final ん) appears in older texts and is still heard in some regional dialects and formal speech. Standard modern Japanese favors the shorter だいぶ in everyday conversation, but both forms are grammatically acceptable and understood nationwide. Learners reading classic literature or watching period dramas may notice だいぶん more frequently, so recognizing it as an alternate form of the same word prevents unnecessary confusion.