Answer:
A sentence is a grammatical unit that consists of one or more words expressing a complete thought. For example: "The cat sat on the mat."
A language construction is a set of rules for constructing sentences in a language. It includes the syntax, grammar, and vocabulary of a language. For example, the subject-verb-object construction in English.
An utterance is a unit of speech or writing produced by a speaker or writer. It can be a single word, phrase, or a complete sentence. For example, "Hi!", "Thank you", or "The sun is shining".
In summary, a sentence is a grammatical unit that expresses a complete thought, a language construction is a set of rules for constructing sentences, and an utterance is a unit of speech or writing produced by a speaker or writer.