Identifying Fragments Part 1

A sentence is a group of words that forms a complete thought. It has both a subject and a verb.

My friends walk along the path.

A sentence fragment is a group of words that does not express a complete thought. It is usually missing a subject or a verb.

Knows the answer.

This is a sentence fragment. It is missing a subject.

Who knows the answer?

She knows the answer.

Now, this is a complete sentence as it has a subject and a verb.