speech balloon

Speech balloons in a 1948 US comic strip

Speech balloons (also speech bubbles, dialogue balloons, or word balloons) are a graphic convention used most commonly in comic books, comics, and cartoons to allow words (and much less often, pictures) to be understood as representing a character's speech or thoughts. A formal distinction is often made between the balloon that indicates speech and the one that indicates thoughts; the balloon that conveys thoughts is often referred to as a thought bubble or conversation cloud.