Meme. Pronounced meem. Think of it as a thought virus or the cultural equivalent of a gene, a phrase, a way of thinking. For instance, the habit of saying "Yo," as in "Yo, Dad, where's my allowance?" might be thought of as an extremely successful, although trivial, meme. The idea of racism would be a more powerful and malevolent meme, while the idea of individual freedom would be a powerful and good meme. One meme that is starting to catch on is the very word "meme."

The best source seems to be "The Selfish Gene," by Richard Dawkins, a 1976 book that argued that an organism was just a gene's way of making more genes. Religion was an immensely forceful meme in Dawkins's view. Daniel Dennett, who picked up the word in his book "Consciousness Explained," sees human consciousness as a collection of memes.

Science fiction writers seem to like the word. Howard Rheingold, for example, wrote a book about the San Francisco technoliterary scene that he subtitled "A Book of Memes." On the Internet, you can now find the Multitasking Extensible Messaging Environment, or Meme, obviously named after the word.

A skeptic might wonder what the notion of a meme adds to the paradigm of cultural evolution. Perhaps there is nothing new under the sun. Plus ca change, plus c'est la meme chose.