If a group of words is not a sentence, what is it? A FRAGMENT.
A fragment is a piece of something larger. Any word or groups of words can be a part of a sentence, but not every group of words IS a sentence. There are two types of fragments:
A PHRASE is a group of words that go together but that is missing a subject, or missing a predicate, or missing both. Because it is missing these items, it cannot express a complete thought
A CLAUSE is a group of words that has a subject AND a predicate; however, it does NOT ALWAYS make a sentence.
Rule of Thumb: PHRASE
Write a sentence, then cross out either the complete subject, the complete predicate, or both of them. The left-over words should make a phrase.
Mike went to the store. --- sentence
Went to the store --- phrase no subject
To the store --- phrase no subject, and no predicate; this is a PREPOSITIONAL PHRASE to is a preposition
The puppy had brightly-colored bows. --- sentence
The puppy --- phrase no predicate
Had brightly-colored bows phrase no subject
Brightly colored bows phrase no subject, no predicate