Beside is a preposition meaning "next to." Besides is a preposition meaning "except" or "in addition to." As a conjunctive adverb, besides means "also."
Examples:
Merdine was too proud to sit beside Gus; besides, she preferred to sit outside.Usage Notes:
- "While the two words were once used interchangeably, beside has been reserved as the preposition and besides as the adverb since the late 18th century. But they are still confounded."
(Bryan A. Garner, Garner's Modern American Usage. Oxford Univ. Press, 2009) - "Some critics argue that beside and besides 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. Using beside 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."
("besides," The American Heritage Dictionary of the English Language, 4th ed., 2000) - "As a number of commentators remark and all conscientious dictionaries show, there is a certain amount of overlap between these two words. The OED shows that historically there was even more than there is now. . . .
"The only question arises when beside is used in the preposition sense of besides. Gould [in 1856] disliked this use, and most commentators since his time simply avoid it by not mentioning it at all. Although it is not nearly as frequent as besides, it is well attested. It has been in use since the 14th century and appears in the King James version of the Bible in several places. Our modern evidence for this sense is modestly literary. . . . While this use of beside is not wrong, nor rare, nor nonstandard, besides is the word most people use."
("beside, besides," Merriam-Webster's Dictionary of English Usage, 1994)
Practice:
(a) Thoreau lived _____ a pond.
(b) Few people _____ his aunt ever visited him.
