When a sentence sentence?

It seems like you're asking "What makes a sentence a sentence?". That's a great question!

Here's the breakdown:

A sentence is a group of words that expresses a complete thought. This thought usually has a subject (who or what the sentence is about) and a verb (what the subject is doing).

Here are some key elements of a sentence:

* Subject: The person, place, or thing the sentence is about. Example: "The cat"

* Verb: The action the subject performs. Example: "slept"

* Complete Thought: The sentence conveys a complete idea. Example: "The cat slept on the couch."

Here are some characteristics that make a sentence grammatically correct:

* Capitalization: Starts with a capital letter.

* Punctuation: Ends with a period (.), question mark (?), or exclamation point (!).

Let me know if you want to explore any of these concepts further or have more examples!