The French conjunctions parce que, car, puisque, and comme are commonly used to draw conclusions or otherwise relate a cause or explanation with a result or conclusion. These conjunctions have similar but not identical meanings and uses.
They fall into the two basic categories of conjunctions; coordinating, which join words or groups of words of equal value; and subordinating, which join dependent clauses to main clauses. Conjunctions of conclusion are one or the other, depending on the conjunction.
Parce Que > Because
Parce que is a subordinating conjunction and can begin a sentence. Parce que introduces a cause, explanation, or motive. It basically explains why something is done.
Je ne suis pas venu parce que mon fils est malade.
I didn't come because my son is sick.
Parce qu'il n'a pas d'argent, il ne peut pas venir.
Because he doesn't have any money, he can't come.
Car > Because, For
Car is a coordinating conjunction, should not begin a sentence, and is mainly found in formal and written French. Car supports a judgment or indicates a reason.
La réunion fut annulée car le président est malade.
The meeting was canceled because the chairman is sick.
David ne va pas venir, car il est à l'université.
David isn't coming, for he is (away) at school.
Puisque > Since, Because
Puisque is a subordinating conjunction and can begin a sentence. Puisque gives an obvious explanation or justification, rather than a cause.
Tu peux partir puisque tu es malade.
You can leave, since you're sick.
Puisque c'était son erreur, il m'a aidé.
Since it was his mistake, he helped me.
Comme> As, Since
Comme is a subordinating conjunction and usually begins a sentence. Comme highlights the link between a consequence and its result.
Comme je lis le plus vite, j'ai déjà fini.
Since I read the fastest, I've already finished.
Comme il est faible, il ne pouvait pas le lever.
Since he is weak, he couldn't lift it.