The key components of a sentence are:
Subject: The main noun or pronoun that the sentence is about (e.g., "The dog" in "The dog chased the ball.")
Predicate: The part of the sentence that tells what the subject is doing or what is happening to the subject (e.g., "chased the ball" in "The dog chased the ball.")
Object: The noun or pronoun that receives the action of the verb (e.g., "the ball" in "The dog chased the ball."). Not all sentences have an object; it depends on the type of sentence and the verb used.