Identify the error in the sentence: Both of the authors is well-known.

The sentence "Both of the authors is well-known" contains a subject/verb agreement error. In this context, the subject is "Both of the authors," which is plural since it refers to more than one author. Therefore, the correct verb form should also be plural. The verb "is" is singular, which creates a discrepancy between the subject and the verb. The correct form of the verb should be "are," resulting in the correct sentence: "Both of the authors are well-known." This highlights the importance of ensuring that the verb matches the subject in number, which is a foundational rule in English grammar.