You may say that hunger gave you no choice but to purloin that side of beef, but a judge would say that you always have a choice between right and wrong, and brand you as a thief. I saw a hungry man...
When it has a subject, verb, punctuation, capitalization, a predicate, and a complete thought. A sentence is a sentence when it is handed down by a judge (or a magistrate).
A sentence is a complete clause with a subject and a finite verb. A sentence fragment is not a complete clause, but is part of a clause (often lacking the verb to make a full sentence). For instance,...