A sentence is a grammatically complete idea expressed in words, while an utterance is any spoken word or sound, not necessarily grammatically or logically complete.

The distinction between a sentence and an utterance lies in the fact that a sentence is a structured set of words conveying a complete thought or idea within the rules of grammar, while an utterance is a vocal expression or a group of spoken words that may not adhere to grammatical rules but still conveys meaning in a particular context.

Sentences can be spoken or written and are used to express statements, questions, commands, or exclamations. An utterance, on the other hand, refers to the act of speaking or expressing oneself. It is the physical realization of a sentence through speech or other forms of communication.