What is a group of words expressing complete thought?

A group of words expressing a complete thought is called a sentence.

Here are some key features of a sentence:

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

* Verb: The action or state of being that the subject performs or experiences.

* Complete thought: The sentence conveys a complete idea or statement.

For example:

* The cat sat on the mat. (Subject: cat, Verb: sat, Complete thought: The sentence tells us what the cat did.)

Let me know if you'd like more examples or explanations!