How to tell them apart
All four describe an event happening immediately after another, but they differ in register and what follows. 途端に is the most everyday and can follow actions or changes of state. や否や, なり, and が早いか are more literary/formal and tend to describe an immediate, often surprising or involuntary reaction. なり specifically attaches to a verb in plain form and stresses the first thing someone did right after, often a sudden personal action. が早いか emphasizes the speed with which the subject moves from one action to the next, typically with the same subject doing both. や否や is used for events that trigger an immediate, often large-scale or dramatic response.
- 途端（に） Use 途端に when you want a common, neutral way to say something happened the instant something else occurred.
- や否や・やいなや Use や否や in formal or written contexts to describe an immediate, often dramatic consequence right after an event.
- なり Use なり to stress the very first action someone took right after doing or experiencing something.
- が早いか Use が早いか to emphasize how quickly the same subject rushed into the next action without hesitation.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| 途端（に） ni | the very instant something happens; right after doing something | N2 |
| や否や・やいなや ya ya yainaya | The instant something happens; immediately after | N1 |
| なり nari | The moment something happens; right after doing | N1 |
| が早いか ga ika | The instant something happens; right after it occurs | N1 |
途端（に） ni
the very instant something happens; right after doing something
途端（に）expresses that something happens the instant another action occurs, often with a surprising or immediate result. It attaches to the past tense (plain past form) of a verb, and に is optional; the pattern is common in both casual and neutral speech.
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暗いトンネルに入った途端、私たちは何も見えなかった。
On entering a dark tunnel, we could see nothing.
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彼女がその本を読み始めたと思った途端、誰かがドアをノックした。
She had hardly begun to read the book before someone knocked at the door.
や否や・やいなや ya ya yainaya
The instant something happens; immediately after
や否や (also written やいなや) means that one action happens immediately after another, with no interval between them. It attaches to the plain (dictionary) form of a verb, and the following clause typically describes an action that occurs at once, often in the past tense.
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トムは目覚まし時計が鳴るや否や、ベッドから飛び起きた。
Tom jumped out of bed as soon as the alarm clock went off.
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彼が部屋にはいるや否や、彼女はわっと泣き出した。
Hardly had he entered the room, when she burst into tears.
なり nari
The moment something happens; right after doing
なり is the plain form of なる, which follows a noun to say that something turns into or reaches that state, as in 夕食の時間になり (it became dinner time). It also appears in set phrases like 使い物になりません (is of no use). It is plain style, so it pairs with です/ます in polite speech.
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私は眠らなければなりません！朝クラスがありますから。
I have to get to sleep! I've got classes tomorrow.
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離婚は現代ではますますありふれたものになりつつある。
Divorce is becoming more common nowadays.
が早いか ga ika
The instant something happens; right after it occurs
が早いか means something happens immediately after another action, with no delay. It attaches to the plain (dictionary) form of a verb and describes two events occurring in rapid succession, as in the bell ringing and students leaving at once. It is a formal, literary expression.
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山の麓に日が昇るが早いかただ一人山を登り始めた。
The sun had barely risen at the foot of the mountain when she set out alone up the slope.
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タクシーと地下鉄、どっちで行くほうが早いかな？
Which is quicker, a taxi or the subway?
途端（に） and や否や・やいなや and なり and が早いか are JLPT N2–N1 grammar points that Japanese learners often mix up. This page compares all 4 side by side on meanings, usage and example sentences, so you can tell them apart.