Lisp differs from almost every other programming language on Earth by using hyphens in its function/variable names. C/Perl/Java/etc. programmers, who can only use hypens for subtraction, like to argue about the relative merits of NamesWithCamelCaseInThem, which are hard to read, or names_with_lots_of_underscores_in_them, which are hard to type. What the debaters rarely mention, it seems, is that neither style is particularly logical.
When you define a function or variable name, you are effectively defining a new word in the vocabulary of your program. Most Western languages allow the definition of “compound words” composed of multiple words. In normal language, these compound words are occasionally mashed together (e.g. “weekend,” “weblog”) but more often left separate (e.g. “dining room,” “miles per hour”).
No programming language parser has yet been written that can understand compound words with spaces in them, so we have to compromise. Western languages, English in particular, already have a compromise in place: they use hypens to form compound words which would be awkward to write as single words or as separate ones (e.g. “all-inclusive,” “president-elect”).
So Lisp’s hyphenated names are not only easier to read than CamelCase and easier to type than underscores, they are actually the most logical choice for creating new compound words. Yet another example of Lisp’s innate superiority. ;)