You use a semicolon when you are making a list, before a transition word or conjunction and to extend a sentence.
If you are using it for entension and before a transition/conjunction, make sure you have two independent clauses to make that sentence.
Ex. My sister also had a cat; she love the pet it.
I'm not giving up; however I sometimes get discouraged.
I traveled to Washington D.C.; Tokyo, Japan; and Moscow, Russia.
