Is the thought complete or incomplete?

Complete thoughts express a full idea.

It must have a subject and verb.

Example: My neighbor fell down the stairs.

An incomplete thought does not make sense by itself. If you walked up to someone and told them an incomplete thought, they would be confused because information is missing.

You can attach incomplete thoughts to a complete thought to form a complex sentence.

Example: Because the floor was wet.

My neighbor fell down the stairs because the floor was wet.