A sentence must have at least one independent clause. A sentence may also contain one or more subordinate clauses.
Subordinate clauses must be attached to an independent clause; they cannot stand alone. If you punctuate a subordinate clause as a complete sentence, you create a fragment.
Here are some examples of fragmented clauses:
Note that each of these subordinate clauses is patterned like a sentence, with both a subject and a verb. However, each begins with a word or words that mark the clause as subordinate (If, Unless, Even though, Which).
Fragmented clauses can be fixed in one of two ways:
If and even though introduce subordinate clauses. The subordinate clauses can be joined to independent clauses to to form complete sentences.
Deleting the words that mark the clauses as subordinate produces complete, independent clauses that can stand as sentences.
Test for fragments
Exercise: Sentence fragments 1
Exercise: Sentence fragments 2
Exercise: Sentence fragments 3
Exercise: Sentence fragments 4
Exercise: Sentence fragments 5
independent clause A word group containing a subject and a verb that can or does stand alone as a sentence.
subordinate clause A word group containing a subject and a verb that cannot stand alone as a sentence because it begins with a word that marks it as subordinate (such as although, because, who, or that).