What is a Word?

Ever since Wordcraft started in 2002, an ongoing question has been, "What is a word?" Unfortunately Bob's essay in that thread now can't be accessed; I'd love to read it again. In Shu's OED link, which still is accessible, the OED staff says, "To determine whether a word has caught on, we normally require several independent examples of the word being used, and also evidence that the word has been in use for a reasonable span of time." Really? Why, then, are there so many words in OED that have only been included in dictionaries or cited once? Wordcrafter tells me there are 14,000 such words. That's really the question behind "epicaricacy." Is it really a word? Even the original citation in Bailey's 1700s dictionary included a very different spelling. Yet, many words have evolved in their spelling, haven't they?

Shouldn't there be a neat, tidy definition of a word? I suppose the best might be its inclusion in OED, but mere mortals make mistakes. Maybe it's just that people use the groups of letters. I don't know, but it has been an ongoing conversation on Wordcraft and will be one here, too. Linguists haven't, I don't think, answered this question. But that's okay because we in the medical sciences haven't answered a lot of questions either.