The term 'PART OF A LONG SENTENCE' is a phrase used to describe a group of words that make up a portion of a sentence. It is usually used to refer to a clause or phrase within a sentence, which can be either independent or dependent. An independent clause is a group of words that contains a subject AND a verb AND expresses a complete thought, while a dependent clause is a group of words that contains a subject AND a verb but does not express a complete thought.