出すSuddenly start doing
出す attaches to a verb stem to show that an action or process begins suddenly, unexpectedly, or with an uncontrolled feel.
What the ending adds
The first verb names the action, while 出す focuses attention on its abrupt beginning. English translations often use “suddenly started,” “burst out,” or simply a natural verb that already suggests a sudden onset.
Typical sudden onsets
Weather, crying, laughter, and motion readily allow the beginning to be noticed as a distinct event.
空が急に暗くなり、雨が降り出した。
The sky suddenly grew dark, and it started to rain.
Analyze赤ちゃんが突然泣き出した。
The baby suddenly burst into tears.
Analyze彼の冗談を聞いた瞬間、みんなが一斉に笑い出した。
The moment they heard his joke, everyone burst out laughing at once.
Analyze止まっていた機械が急に動き出しました。
The machine, which had been still, suddenly started moving.
AnalyzeIntentional actions
A person can deliberately perform the action, but the context should still present its beginning as abrupt or unexpected. Without that context, the neutral expression for “begin doing” is usually safer.
私の顔を見た瞬間、彼は早口で話し出した。
The moment he saw my face, he suddenly began speaking rapidly.
AnalyzeSpeaking is intentional, but the timing makes its onset feel abrupt.
Sudden onset versus neutral beginning
始める neutrally says that an action begins. 出す adds a noticeable sense of suddenness, unexpectedness, or weak control. Do not replace every English use of “start” with the latter form.
Negative form
雷は鳴ったが、雨はなかなか降り出さなかった。
There was thunder, but the rain did not start for quite a while.
AnalyzeThe negative says that the expected onset failed to occur during that period.
More examples
風が強くなり、窓ががたがた鳴り出した。
The wind grew stronger, and the windows suddenly began rattling.
Analyze暗い道で、犬が突然ほえ出した。
On the dark road, a dog suddenly began barking.
Analyzeその知らせを聞くと、彼の手が震え出した。
When he heard the news, his hands began to tremble.
Analyze子どもは母親を見つけると、急に走り出した。
When the child spotted their mother, they suddenly started running.
Analyze観客は静かに待っていたが、一人が急に歌い出した。
The audience had been waiting quietly, but one person suddenly began to sing.
Analyze空は急に暗くなりましたが、雨は降り出しませんでした。
The sky suddenly grew dark, but it did not start raining.
Analyze