weil clauses

weil means because. It also does something dramatic: everything after it stops being a main clause, and the conjugated verb drops to the very end.

Main clause · comma · weil · subject · … · conjugated verb (end).

• Ich muss schlafen, weil ich müde bin.

  I have to sleep because I am tired.

  bin goes last

• Ich lerne Deutsch, weil meine Frau Deutsche ist.

  I am learning German because my wife is German.

• Ich trinke Kaffee, weil ich müde bin.

  I drink coffee because I am tired.

Now the part worth slowing down for. When the weil-clause contains a modal, the infinitive is already at the end — so the modal goes behind it. Two verbs at the end, modal last.

• Ich kann heute nicht kommen, weil ich arbeiten muss.

  I cannot come today because I have to work.

  arbeiten · muss — modal last

• Ich gehe nach Hause, weil ich schlafen will.

  I am going home because I want to sleep.

• Ich lerne heute, weil ich morgen nicht lernen kann.

  I am studying today because I cannot study tomorrow.

The comma before weil is not optional in German — it is a spelling rule, not a stylistic choice.