Every complete sentence has two essential parts: the subject (who or what is doing something) and the predicate (what the subject is doing or being). The subject tells what the sentence is about; the predicate tells what action is happening or what state the subject is in. Both parts are necessary for a sentence to be complete.
Identify the subject by asking "Who or what is this sentence about?" and the predicate by asking "What is that subject doing or being?" Practice with simple sentences before moving to complex ones.
Every complete sentence is built on a conversation between two things: something that is being talked about, and something being said about it. We call these the subject and the predicate. The subject answers the question "Who or what is this sentence about?" The predicate answers "What about it?" — what the subject does, is, or has done to it. This two-part structure is the skeleton beneath every English sentence, from the simplest ("Dogs bark") to the most elaborate ("The ancient stone bridge spanning the river collapsed last Tuesday").
The easiest way to find the subject is to find the main verb and then ask who or what is performing that action or being described. In "The tired students finished the exam," the verb is "finished" — who finished? "The tired students." That whole noun phrase is the subject, not just "students." The predicate is everything else: "finished the exam." Notice that the subject is the whole phrase, not just the head noun. "Tired" is part of the subject because it modifies "students" — they travel together.
This is where the most common confusion arises: students often think the subject is just the first noun or the first word. But subjects can appear in unusual positions, and they always include all the words that belong to the noun phrase. "Into the room walked three tall strangers" — the subject is "three tall strangers," not "room," which is part of a prepositional phrase that happens to come first. The subject is the actor (or topic), wherever it sits in the sentence.
The predicate is not just the verb — it includes the verb and everything that completes or extends it: objects, complements, and modifiers. In "She gave her sister a beautiful gift," the predicate is "gave her sister a beautiful gift" — that entire phrase says what she did. Understanding the predicate as a complete unit prepares you to recognize direct objects, indirect objects, and predicate adjectives, which are all parts of the predicate. Mastering subject-predicate structure gives you the foundation to diagram, analyze, and write sentences of any complexity.