て / で

The て-form can give a cause: the first part says what happened, the second what came of it. A verb takes its て-form, an い-adjective changes its final い to くて, and a な-adjective or a noun takes で.

て or から

A て-form cause cannot lead into a request, an order, an invitation or something you have decided to do. Those need から or ので.

• × 危なくて、気をつけてください → 危ないから、気をつけてください
• × 暑くて、窓を開けましょう → 暑いから、窓を開けましょう

Feelings and "can't"

The commonest second part is a feeling, or a potential form saying what you could not do. English often turns these into "so … that".

Usage notes

These go beyond a positive verb or adjective as the cause.

A negative cause

ない becomes なくて: "because I didn't", "because there wasn't".

A noun as the cause

With an event noun – an accident, an illness, an earthquake – で alone gives the cause, with no verb.