Tanya trusts others beside her best friend. Do I need an "s" after beside?

Yes.

http://dictionary.reference.com/browse/besides

You're welcome.

Thank you for confirming.

No, you do not need to add an "s" after "beside" in this sentence. The word "beside" is a preposition, and in this case, it is used to indicate that Tanya has trust in people who are not her best friend. When used as a preposition, "beside" does not require any additional pluralization. Here's how you can confirm:

1. Look closely at the sentence structure:
- "Tanya trusts others" is the main phrase, where "others" is plural, indicating more than one person.
- "beside her best friend" is a prepositional phrase that describes the relationship between Tanya and the people she trusts.

2. Examine the function of "beside" in the sentence:
- "Beside" is used to show that Tanya trusts people who are in addition to or apart from her best friend.
- It functions as a preposition, which does not change its form based on the number of nouns it relates to.

Therefore, there is no need to add an "s" after "beside" in this sentence.