The major difference between a sentence and an utterance is

There is much difference between these two linguistic terms,but the most significant difference between a sentence and an utterance is in that sentences are judged according to how well they make sense grammatically,while utterances are judged according to their communicative validity.
这是语言学的两个概念,主要的区别就在于句子必须是强调在语法上要成立的,而表达（utterance）主要强调交流上无障碍.
你这个问题其实可以拿到语言学下面的版块哦~