A complete subject in a sentence is composed of the main noun or simple subject that the sentence is about and all the words that describe it. The complete subject is one of the basic parts of a sentence, and the other part is the predicate that contains the verb.
The simple subject is the most-important part of the complete subject and cannot be part of a prepositional phrase. The prepositional phrase begins with a preposition and usually ends in a noun, which should not be mistaken to be the subject. A simple subject typically appears before the verb, but there are exceptions.