Q: When describing three people working together, is it a collaboration among, amongst, or between them?
A: There’s no difference between “among” and “amongst,” beyond their spellings. “Among” is preferred in American English and “amongst” is often preferred in British English. I wrote a blog entry earlier this year about “among/amongst.”
You also ask about the use of “between” versus “among.” In general, “between” applies to two (“This is between him and me”), and “among” to three or more (“The six members agreed among themselves”).
But “between” can be used in reference to a collection, if the members or items or whatever are related to each other individually as well as to the group.
The New York Times Manual of Style and Usage gives this example: “Trade between the United States, Canada, and Mexico has grown under Nafta.”
As the style guide explains, “Each country trades with each of the others, rather than with all simultaneously. When more than two things are related in a purely collective and vague way, use among.”
The word “betwixt,” by the way, is an old-fashioned version of “between,” though both words have been around in various forms since Anglo-Saxon times.
The Oxford English Dictionary describes “betwixt” as somewhat archaic in literary English and chiefly poetical.
However, the expression “betwixt and between,” meaning neither one thing nor the other, is a relative newcomer.
The earliest citation in the OED is from Frederick Marryat’s maritime novel Newton Forster (1832), which refers to “the lease of a house in a betwixt and between fashionable street.”