"Thought balloon" is a term often used in comic strips and graphic novels to represent a character's inner thoughts. However, there are several other synonyms that can be used to convey the same idea. Some of the most common alternatives are "speech bubble," "thinking cloud," "mind bubble," "thought cloud," and "thought bubble." These phrases are all essentially interchangeable, and artists and writers often choose which one to use based on personal preference or style. Ultimately, all of these terms serve the same function, to provide a visual cue for the reader to understand what a character is thinking, feeling, or saying internally.