Some critics argue that beside
should be kept distinct when they are used as prepositions. According to that argument, beside
is used 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 besides
should be used: Besides replacing the back stairs, she fixed the broken banister. No one besides Smitty would say a thing like that.
But this distinction is often ignored, even by widely respected writers. While it is true that besides
can never mean at the side of, beside
regularly appears in print in place of besides.
in this way can be ambiguous, however; the sentence There was no one beside him at the table
could mean that he had the table to himself or that the seats next to him were not occupied. See Usage Note at together