How can I identify a sentence fragment?
At its simplest, a sentence contains a subject and a verb (e.g., “Sarah woke up”). If there is no verb, or no subject, then it’s usually a sentence fragment.
Another way of testing whether you’re dealing with a sentence fragment is to ask yourself if it expresses a complete thought. If it doesn’t, then it is a sentence fragment (e.g., “No luck today”).
Look for clauses that leave you needing more information to fully understand them (e.g., “Yesterday at the hospital”).