A semicolon connects two independent but related clauses, or thoughts.
When To Use a Semicolon: If the two clauses could stand on their own as two complete sentences. Note: Use sparingly! One a paragraph at absolute most. Too many semicolons can interrupt the flow of an essay.
Do Not: Use a semicolon with conjunctions (and, but, or, nor, yet, etc.).
CORRECT: My baby sister has cried every night this week; I've hardly slept in days.
INCORRECT: I didn't feel like doing my homework; so I went for a jog instead.