'Race' and 'ethnicity': Readers want to know

Or at least one of them does. She (he?) writes:

Hello Mr. Fox:

I read and enjoyed your article in the L.A. Times entitled 'Minority Groups' Have Outgrown Their Labels which I clipped and saved. I recently came across it again while thumbing through my�files and I would like to get your opinion on the following:

What is the difference between race and ethnicity?

Thank you for your time and opinion.

And I answered:

Hmm. This may require a little thought to put it simply and briefly. Maybe I'll put something about it up on my weblog. Usually, when people speak of human "races," they are talking about biology, especially those most noticeable physical differences between groups of people (skin color, hair texture, and so on). "Ethnicity" (I just looked this up) comes from the Greek word for a "people," in the sense of a national group. Like most sociologists and anthropologists, I use the word to refer to culture. So, in the case of people from Spanish-speaking countries, they may be of many different races, but when they come to the US, they discover that they have a lot of culture in common (language is the big thing, but soccer, experience with the Catholic church -- even if they are not in it -- and certain attitudes that have been carried over, generation through generation, from Spain). In my book, Hispanic Nation, I argue that many of these people are working together (despite the obvious differences in skin color, Spanish accent, cooking preferences and so on) to create a new ethnicity, which is what I call the "Hispanic nation" of the US.

... Anyway, if you're curious, I've written a lot more on the topic in that book, Hispanic Nation.