A compound sentence is a sentence in which two simple sentences are joined together with a conjuncion. Use a comma to separate the two simple sentences in a compound sentence.
I ride my bike. John rides a scooter.
I ride my bike, but John rides a scooter.
The comma goes right before the the word but. The word but is a conjunction. It joins the two simple sentences together.
Here is another example:
Mom likes apple pie. Dad likes cherry pie.
Mom likes apple pie, and Dad likes cherry pie.
The word and is a conjunction joining the two simple sentences into one compound sentence. Use a comma before the word and.
Use a comma in front of a conjunction when joining two simple sentences into a compound sentence.
▶It’s your turn. Place a comma in this sentence. The day is sunny but the wind is cool. Did you put the comma right before the conjunction but? Good for you!