つい means doing something inadvertently or on impulse; うっかり emphasizes a lapse of attention. つい can fit an unplanned purchase or remark, while うっかり commonly fits forgetting or overlooking something. Their meanings overlap, so neither always identifies a single psychological cause.
つい・うっかり · also tsui / ukkari / ついつい / うっかりして
つい — I couldn't help it; before I knew it · うっかり — carelessly, by an oversight · ついつい — the emphatic つい
Sentences
つい · the impulse you lost to
plain past。
Hover, tap, or tab through the words.
つい
つい ［1］
before I could stop myself
adverb · resistance failed, and the speaker admits wanting it
Ask Rikai
全部
ぜんぶ ［1］
all of it
noun used adverbially · the extent of the damage
Ask Rikai
食べ
たべ
eat
stem of 食べる · joining to ちゃった
Ask Rikai
ちゃった
ちゃった
and I regret it
contraction of てしまった · the regret that つい implies
Ask Rikai
I ended up eating the whole thing.
うっかり · attention slipped
polite。
Hover, tap, or tab through the words.
会議
かいぎ ［1,3］
meeting
noun · a formal meeting rather than a chat
Ask Rikai
の
の
links noun to noun
particle · A の B = B belonging to A
Ask Rikai
こと
こと
the act of; the fact of
noun · turns the verb in front into a noun
Ask Rikai
を
を
marks the direct object
particle · pronounced お
Ask Rikai
うっかり
うっかり ［3］
carelessly; it slipped my mind
adverb · attention lapsed, no impulse involved
Ask Rikai
忘れて
わすれて
forgot and
て-form of 忘れる · linking into しまいました
Ask Rikai
しまいました
しまいました
(regrettably)
polite past of てしまう · the formal version of ちゃった
Ask Rikai
I completely forgot about the meeting.
つい · saying too much
plain past。
Hover, tap, or tab through the words.
つい
つい ［1］
before I knew it
adverb · the mouth moved ahead of the judgement
Ask Rikai
余計
よけい ［0］
unnecessary; more than needed
な-adjective · the extra that should not have been said
Ask Rikai
な
な
(attributive)
な-adjective ending · required before the noun
Ask Rikai
こと
こと
the act of; the fact of
noun · turns the verb in front into a noun
Ask Rikai
を
を
marks the direct object
particle · pronounced お
Ask Rikai
言っちゃった
いっちゃった
said it
言って ＋ しまった, contracted · the regret is built in
Ask Rikai
I let it slip without thinking.
うっかりして · the workplace apology
polite、。
Hover, tap, or tab through the words.
すみません
すみません
I'm sorry
expression · the standard apology
Ask Rikai
うっかり
うっかり ［3］
not paying attention
adverb · admitting a lapse rather than a temptation
Ask Rikai
して
して
doing
て-form of する · うっかりする, to be careless
Ask Rikai
いました
いました
was (in that state)
polite past of ている · the carelessness lasted a while
Ask Rikai
I'm sorry — I wasn't paying attention.
ついつい · the habit you keep losing to
plain。
Hover, tap, or tab through the words.
夜
よる ［1］
night
noun · the time of day, used adverbially with は
Ask Rikai
は
は
as for — the topic
particle · written は, read わ
Ask Rikai
ついつい
ついつい
I keep doing it
doubled つい · emphatic, and clearly about a habit
Ask Rikai
スマホ
スマホ
phone
noun · clipped from スマートフォン
Ask Rikai
を
を
marks the direct object
particle · pronounced お
Ask Rikai
見て
みて
looking at
て-form of 見る · linking into しまう
Ask Rikai
しまう
しまう
end up doing
plain てしまう · the habit continuing into the present
Ask Rikai
I keep ending up on my phone late at night.
うっかり · the wrong train
plain past。
Hover, tap, or tab through the words.
うっかり
うっかり ［3］
carelessly
adverb · a lapse, with no wish to board the wrong train
Ask Rikai
急行
きゅうこう ［0］
express train
noun · the train that skips the stop you wanted
Ask Rikai
に
に
to; at; into
particle · a point something reaches — a place, a time, a person, or a state
Ask Rikai
乗って
のって
got on and
て-form of 乗る · takes に for the vehicle
Ask Rikai
しまった
しまった
(regrettably)
plain past of てしまう · the mistake is done
Ask Rikai
I wasn't thinking and got on the express.
Forms
つい＋食べた / 言った / 買った
つい食べちゃった. I ate it before I could stop myself. Almost always past — it is a confession.
うっかり＋忘れた / 間違えた / 落とした
うっかり忘れた. It slipped my mind. The failure is attention, not willpower.
つい〜＋ちゃった
The natural pairing. てしまう carries the regret that つい is already implying.
うっかりして＋the mistake
うっかりしていました. I wasn't paying attention — a complete apology on its own, and usable at work.
Meaning
つい admits you wanted to. The impulse was there and your resistance failed. That is why it fits eating the last piece, saying the thing you should not have said, and buying what you did not need.
うっかり admits nothing of the kind. There was no impulse — attention simply lapsed. Forgetting, misreading, getting on the wrong train. Using つい here would imply you were tempted to forget, which is nonsense.
思わず is faster than either. A reflex before thought arrives: 思わず笑ってしまった, I laughed before I could stop it. No habit behind it, and no lapse — just a body reacting first.
They excuse different things, so they clear you of different charges. つい says my self-control failed; うっかり says my attention did. At work the second is the safer admission, which is why うっかりしておりました exists as a fixed apology and つい does not.
Inside the words
The same つい appears in ついさっき, just a moment ago, and ついでに, while I'm at it. The thread is proximity — the action was right there, so it happened.
The doubled consonant marks it as the same family as ぼんやり and ぼうっと — words for attention that is not where it should be. There is no kanji, and none is wanted.
Each is a confession, and てしまう is the grammar of regret. つい〜ちゃった and うっかり〜てしまいました are so standard that the つい or うっかり can feel redundant — it is not, it names which failure it was.
Watch out
This says you were tempted to forget, which is not a thing. Forgetting is an attention failure: うっかり忘れた.
Unless you genuinely did not notice what you were eating, the honest word is つい. うっかり here reads as dodging the fact that you wanted it.
It admits you failed to resist, which invites the question of why you tried so little. うっかりしておりました is the established formula and does not raise that.
Also asked
つい is an impulse you failed to resist — you wanted to. うっかり is an attention lapse — you were not thinking about it at all. Only the first admits to wanting it.
Because it implies a temptation to forget. Forgetting is not something you are drawn to do, so it takes うっかり.
Emphasis, and a clear sense of habit — this keeps happening and you keep failing to stop it. ついついお菓子を食べてしまう is a standing weakness, not one slip.
思わず is a reflex that beats thought — laughing, flinching, crying out. つい involves a resistance that existed and lost, usually to a habit.
うっかりしておりました or 確認を怠りました. つい concedes that you did not try hard enough to resist, which is not what you want on record.
Not strictly, but both are confessions and てしまう supplies the regret, so the pairing is extremely common. つい買っちゃった and うっかり忘れてしまいました are the natural shapes.
References
Shogakukan dictionaries via Kotobank: つい — inadvertent action and temporal closeness
Shogakukan dictionaries via Kotobank: うつかり — inattention and accidental action
Nearby
That's the whole list. rikAI is an iPhone app and it isn't out yet.
See what rikAI does · How it works · All grammar points · Language concepts
