Bottle cap, the small circular object that seals a bottle, can be referred to by a multitude of synonyms. It can be called a screw cap, jar top, lid, closure, stopper, crown cap, twist off cap, cork, or plug. These synonyms vary depending on the type of bottle cap being used. Twist off, for example, refers to a cap that can be removed by a simple twisting motion. Crown cap often refers to the metal caps found on soda bottles. Stopper is commonly used for cork bottle caps. Regardless of the synonym used, the function of a bottle cap remains the same: to keep liquids in the bottle sealed and fresh.