Here's why:
* Compound Subjects: These are two or more nouns or pronouns joined by a conjunction like "and" or "or," working together as a single subject. Example: "The cat and the dog are playing."
* Phrases as Subjects: A group of words that acts as a single subject, often containing a noun or pronoun. Example: "The beautiful, blue sky is clear."
Important Note: While a subject can be multiple words, it must function as a single unit grammatically. It needs to agree with the verb in number (singular/plural).