The choice between "is" and "are" depends on the subject of the sentence. Both are forms of the verb "to be," but they are used in different contexts based on whether the subject is singular or plural.

1. Use "is" when the subject is singular.

   • Example: "The cat is sleeping."
   • Here, "cat" is singular, so "is" is correct.

2. Use "are" when the subject is plural.

   • Example: "The cats are sleeping."
   • Here, "cats" is plural, so "are" is correct.

3. Exceptions:

   • Collective nouns (e.g., "team," "family") can take "is" or "are" depending on whether the group is acting as a single unit or as individuals.
     • Example: "The team is winning." (The team as a whole.)
     • Example: "The team are arguing." (The individuals within the team.)
   • Indefinite pronouns like "everyone," "someone," and "nobody" are singular and take "is."
     • Example: "Everyone is here."

If you provide a specific sentence, I can help you determine whether "is" or "are" is correct!