Some people argue that these two words should be kept distinct when they are used as prepositions. By this thinking, you should use beside only to mean “at the side of,” as in There was no one in the seat beside me. For the meanings “in addition to” and “except for” you should use besides: Besides replacing the back stairs, he fixed the broken bannister. No one besides Smitty would say a thing like that. But this distinction is often ignored by widely respected writers.

While it’s true that besides can never mean “at the side of,” you will often see beside used in place of besides in print. Watch out for ambiguity when using beside in this way. The sentence There was no one beside me at the table could mean that you had the table to yourself or that the seats next to you were not occupied