first portion of the alimentary canal that receives food

The mouth is an opening in the face and is the first part of the alimentary canal (digestive system). It is the place where food is chewed. The mouth has teeth to help eat/chew the food.

A closed human female mouth
For the geographical meaning of mouth see River

In addition to its main role as the start of the digestive system, in humans the mouth also plays a great part in communication. The tongue, lips, and jaw, which are parts of the mouth, are needed to produce the number of sounds in human language. People also kiss and show their feelings with the mouth.