A sentence fragment is just what it sounds like: a fragment, or piece, of a real
sentence. As you can probably guess, teachers and instructors don't appreciate
parts of sentences - they want the whole thing!
A full sentence is made up of a subject and a predicate. Simply put, a subject
is who or what the sentence is about, and the predicate is what the subject
is or is doing. The predicate will have a verb in it (although it
can be a linking verb, like "is" or "was"). A sentence must have both a subject and
a predicate, or it is a fragment.
You might be surprised by what qualifies as a sentence and what doesn't. For instance,
the following example is a sentence:
He worries.
There's a subject ("he") and that subject is doing something ("worries"), a verb
that here serves as a one-word predicate. So "He worries" is a complete sentence.
But the following example is a fragment:
The 17-year-old girl with the long, beautiful hair, green eyes, and fast car.
Although this is a very detailed description, it is still a fragment because it
only talks about and describes the girl (the subject): it doesn't tell us what "the
17-year-old girl with the long, beautiful hair, green eyes, and fast car" IS or
IS DOING. There needs to be a predicate that follows the subject: "The 17-year-old
girl with the long, beautiful hair, green eyes, and fast car is a Russian spy" or
"The 17-year-old girl with the long, beautiful hair, green eyes, and fast car likes
to go ice-skating."
But here's a trickier one:
While he was worrying himself to death about his little lost dog and calling the
police.
Even though there seems to be a subject ("he") and two verbs ("was worrying" and
"was calling"), this is definitely a fragment. That's because this is a dependent
clause - a fancy phrase that means that this phrase cannot stand alone as a sentence,
but needs to have a real sentence to which it can attach itself.
Let's make it a real sentence:
While he was worrying himself to death about his little lost dog and calling the
police, Harry completely lost track of the time.
You can see here that the real sentence - otherwise known as an independent clause,
because it can stand all by itself - is "Harry completely lost track of the time."
It has a subject and a predicate. The dependent clause "While he was worrying and
calling the police" only describes the sentence and gives it more detail.
As you can see from the example above, you have to watch out for fragments that
begin with subordinating conjunctions. Subordinating conjunctions are certain
words that signal to you, "Hey, this is the beginning of a dependent clause that
can't stand by itself as a sentence!" "While" is one of those words. Here are some
others: after, although, as, because, before, how, if, once, since, than, that,
though, until, when, where, whether, and while. When you see a sentence beginning
with one of those words, make extra certain that there is an independent clause
- or full sentence - to go with it, or you've got yourself a fragment!