The first thing that comes to mind when you think of your mouth is probably eating - or kissing! But your mouth's a lot more than an input slot for food or a tool for smooching your sweetie. Your mouth and teeth form your smile, which is often the first thing people notice when they look at you. The mouth is also essential for speech: The tongue (which also allows us to taste) enables us to form words with the help of our lips and teeth. The tongue hits the teeth to make certain sounds. The th sound, for example, is produced when the tongue brushes against the upper row of teeth. If a person has a lisp, that means the tongue touches the teeth instead of directly behind them when saying words with the s sound