急に vs 突然
JLPT N3 vocabulary · what is the difference?
Both mean "suddenly" and in many sentences either is fine. The difference is that 急に focuses on a rapid change of state you notice or experience (急に寒くなった — it turned cold all of a sudden), while 突然 presents an abrupt event that breaks in with no warning (突然電話が鳴った). For things that change or speed up, use 急に; for out-of-the-blue events, 突然 is stronger.
When to use each
急に
きゅうに
Use 急に for a change that happens faster than expected — weather, mood, health, plans, speed. It pairs naturally with change verbs like なる, 変わる, 増える and 止まる, and with 急に用事ができる for plans that come up at short notice.
急に寒くなりましたね。
きゅうにさむくなりましたね。
It's turned cold all of a sudden, hasn't it?
急に用事ができて、行けなくなりました。
きゅうにようじができて、いけなくなりました。
Something came up at short notice, so I can't go any more.
突然
とつぜん
Use 突然 for an event that arrives with no warning at all; it is more emphatic and a little more written-sounding than 急に. It also modifies a noun with の — 突然の雨, 突然の知らせ — which 急に cannot do (that form is 急な).
突然、後ろから名前を呼ばれた。
とつぜん、うしろからなまえをよばれた。
Suddenly someone called my name from behind.
突然の知らせに驚きました。
とつぜんのしらせにおどろきました。
I was shocked by the sudden news.
Sentences where only one works
急に暑くなってきた。
きゅうにあつくなってきた。
It's suddenly getting hot.
A change of state along a scale, so 急に. 突然暑くなった is possible but sounds as if the heat switched on in an instant.
突然ドアが開きました。
とつぜんドアがひらきました。
The door suddenly flew open.
A one-moment event with no warning — 突然 is the natural choice and carries the surprise. 急に開いた is acceptable but weaker.
突然の雨でびしょ濡れになった。
とつぜんのあめでびしょぬれになった。
I got soaked in a sudden downpour.
Modifying a noun directly needs 突然の; 急に cannot do this, and you would have to say 急な雨.
車が急に止まった。
くるまがきゅうにとまった。
The car stopped abruptly.
急に also carries the "sharply, at speed" sense that ties back to 急ぐ, which suits movement. 突然止まった shifts the focus to how unexpected it was.
Common mistakes
急にの雨が降った。
突然の雨が降った。／急な雨が降った。
急に is already an adverb and cannot take の. Before a noun use 急な or 突然の.
突然寒くなってきました。(as small talk about the season)
急に寒くなってきました。
Not ungrammatical, but for weather turning over a day or two, 急に is what people actually say; 突然 overstates it as if the temperature dropped in one instant.
Frequently asked questions
Are 急に and 突然 interchangeable?
In a large number of sentences, yes — 急に雨が降り出した and 突然雨が降り出した are both fine and mean nearly the same thing. The reliable differences are grammatical: only 突然 takes の before a noun, and 急に is the one used for changes along a scale like temperature or speed.
Which one is stronger?
突然. It implies no warning whatsoever and is the one used for shocking news or events. 急に can simply mean "sooner than expected".
Is いきなり the same?
いきなり is close to 突然 and more casual and spoken. It often carries a hint of complaint that something skipped the expected build-up, as in いきなり呼ばれた.