In this sentence, what is the error: The doctor and nurse works late on weekends to help patients?

The focus of the error lies in the word "works." The subject of the sentence, which is "The doctor and nurse," is a compound subject consisting of two singular nouns. When a subject is compound and joined by "and," it requires a plural verb form. Therefore, instead of "works," the correct verb form should be "work" to properly agree with the plural subject. Using "work" conveys that both the doctor and nurse perform the action of working late on weekends together.