Each sentence must have a subject. The subject of a sentence is the person or thing that the sentence is about. The subject of a sentence is usually doing something.
The dog chewed on a bone.
In this sentence, the subject is dog. The sentence is about the dog, and the dog is doing something: chewing.
Sometimes a sentence has more than one subject.
Bob, Jan, and Missy are riding their bikes to the park.
This sentence is about three people – Bob, Jan, and Missy. The three people are doing something together – riding.
When several nouns are all together as the subject of the sentence. we call it a compound subject.
Here are more examples of sentences with a compound subject:
Our dog, a squirrel, and three birds are all in the yard right now.
The police man, the suspect, and a newspaper reporter gathered in a room at the police station.
Mom and Dad are driving tonight to pick up my sister from college.
Sometimes a sentence has a compound subject. In that case, the sentence is about more than one person or thing.
▶ Now you try it. Find the compound subject in this sentence: The dog and the cat are friends. Did you find two nouns that are doing something in this sentence? Good for you!