weil meaning and definition in german

In formal writing, weil is always a subordinating conjunction, i.e. the following clause is a subordinate clause and has the respective word order (see example above). In the beginning of a sentence, weil is preferably replaced with da: Da ich krank bin, kann ich nicht kommen.
In colloquial German, no such restrictions apply. Weil can thus be coordinating as well as subordinating. In the former case, it replaces standard denn: Ich kann nicht kommen, weil ich bin krank. The conjunctions denn and da are both relatively infrequent in colloquial German.