急にkyuu ni“suddenly; all at once”

急に (きゅうに) means “suddenly” or “all of a sudden.” It is a JLPT N4 adverb for changes and actions that come without warning: 急に寒くなった — “It suddenly got cold.”

急 is a な-adjective meaning “sudden,” “urgent,” or “steep.” Like every な-adjective, it turns into an adverb with に. So 急に is simply the adverb form of 急, and you will see the other forms too: 急な用事 (an urgent errand), 急な坂 (a steep slope), 急だね (that’s sudden).

急に marks a break: things were one way, and then, with no warning, they were another.

What does 急に mean?

急に tells you that a change happened quickly and without a lead-up. Before, the situation was stable; then something switched.

• 急に雨が降り出した。 — It suddenly started raining.
• 電車が急に止まった。 — The train stopped abruptly.
• 予定が急に変わった。 — The plans changed at short notice.

The English translation shifts with context: “suddenly,” “abruptly,” “all at once,” “out of nowhere,” or “at short notice” for plans and schedules. What stays the same is the contrast between before and after. That is why 急に loves verbs of change: 〜くなる, 〜になる, 変わる, 止まる, and the compound 〜出す.

How to form 急に

急に is an adverb, so it doesn’t attach to anything. Put it before the verb or verb phrase it describes, usually right after the subject or at the start of the sentence.

Both word orders are natural: 急に雨が降り出した and 雨が急に降り出した. Putting 急に first highlights the surprise; putting it after the subject focuses on what that subject did.

When is 急に used?

• Weather and temperature: 急に寒くなる, 急に晴れる, 急に風が強くなる.
• Movement stopping or starting: cars braking, people stopping in the street, trains halting.
• Changes of plan: 急に会議が入った, 急に行けなくなった. This is extremely common at work and between friends.
• Feelings and health: 急に頭が痛くなった, 急に悲しくなった.
• Complaints: 急に言われても… (“You can’t just spring this on me…”) is a set phrase for pushing back on short notice.

急に is neutral in register. You can use it in casual talk, in polite speech with ます, and in written narration.

急に example sentences

Look at what follows 急に in each sentence: a change of state (寒くなる, 静かになる), a start or stop (降り出す, 止まる), or a change of plan (変わる). That is the natural territory of this adverb.

Nuance of 急に

急に implies that the change was faster than it should have been. When the weather gets cold gradually over November, you say だんだん寒くなった. When it drops ten degrees overnight, you say 急に寒くなった. The adverb puts the two states side by side and stresses how little time separated them.

That also gives 急に a slight inconvenienced feeling in social contexts. 急に予定が変わった hints that the change caused trouble, and 急にごめんね (“sorry for the short notice”) is a natural way to apologise when you contact someone without warning.

💡 Don’t mix up 急に and 急いで. 急いで is the て-form of 急ぐ (to hurry) and means “quickly, in a hurry.” 急いで歩く = walk fast. 急に歩く = suddenly start walking (and sounds odd on its own).

急に vs 突然

突然 (とつぜん) also means “suddenly,” and in many sentences you can swap the two. The difference is in what they focus on and where they sound natural.

Use 急に for things that change, especially temperature, mood, and plans. Use 突然 for single surprising events: a phone call in the middle of the night, a blackout, a stranger appearing. Notice the modifiers too: 急な雨 and 突然の雨 are both correct, but never 急の雨. 急に is also the adverb you will see most often right before 〜出す.

Common mistakes with 急に

Is 急に on the JLPT?

A classic usage question offers four sentences with 急に and asks which one is natural. The wrong ones typically use it to mean “quickly” (急に食べてください) or put it before a noun without な.

Practice questions for 急に

Learning path for 急に

Related grammar to review next

• 出す — the verb ending that most often follows 急に, for actions that burst out.
• なる — 急に寒くなる and 急に静かになる are built on this change verb.
• てくる — describes change that builds up gradually, a useful contrast with 急に.
• ようになる — for changes in habits and abilities, which can happen 急に or slowly.

Learn 急に with Hane

Hane teaches 急に with the verbs it naturally pairs with, like 〜くなる and 〜出す, and drills it against 急いで so you stop mixing them up. Practise N4 grammar in Hane.