What Makes a Sentence a Sentence (or not)
Noun or Verb
100

Each one has a subject and a verb working together to express an idea.

What is a sentence.

100
The word "Marshall" in the sentence "Marshall rides his bicycle. 

What is the subject?

200
It's always a noun or pronoun.

What part of speech is the subject of a sentence? 

200

The part of speech of the word "Marshall."

What is a noun? 

300

It doesn't have a subject and verb working together. It doesn't express a complete idea.

What is a fragment?

300

The kind of noun that "Marshall is," the kind of noun that is capitalized because it's a special name. 

What is a proper noun? 

400

This is what we call the word for what the subject does or what the subject is.

What is a verb?

500

When two separate sentences are joined with no punctuation a comma (the wrong punctuation) between them.

What is a run-on sentence?