〜て、〜（理由）
The て-form linking cause and effectmachine translation
FormationVerb/adjective て-form + clause stating the result
Besides linking sequential actions, the て-form can also gently link a cause to its result: ニュースを聞いて、びっくりしました (hearing the news, I was startled). Adjectives work too: 頭が痛くて (because my head hurt…), and nouns and な-adjectives use で: 病気で (because of illness…), にぎやかで (because it was lively…).
This pattern has one important restriction: the second clause is usually an emotion, a state, or something beyond one's control — びっくりする, うれしい, 困る, 疲れる, 〜られない. The second clause cannot be a command, an invitation, or the speaker's intention; sentences like "because…, please do / I plan to do" must use から or ので instead.
Compared with から・ので, the て-form states the reason more faintly — it simply lets the two clauses flow together, leaving the listener to infer the cause-and-effect. When you want to state the reason clearly and emphatically, use ので (learned in the N4 complex-sentence section).
Examples
ニュースを聞いて、びっくりしました。
Hearing the news, I was really surprised.
頭が痛くて、学校を休みました。
I had a headache, so I stayed home from school.
友達に会えて、うれしかったです。
I was so happy to get to see my friend.