Question

when do we put a comma ?

Answer 1

Use a comma before any coordinating conjunction (and, but, for, or, nor etc) so, yet) that links two independent clauses.
Use a comma after a clause that starts a sentence.
Use a comma in direct speech after pauses, and before the double quote marks.

Answer 2

We use a comma after the first independent clause when you link two independent clauses with one of the following coordinating conjunctions: and, but, for, or, nor, so, yet......

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