Sorry, I hit the send button before I finished.

Race is a false classification of people that is not based on any real or accurate biological or scientific truth. In other words, the distinction we make between races, has nothing to do with scientific truth.

Race is a political construction. The concept of race was created by Europeans as a classification of human beings with the purpose of giving power to European colonizers, and to legitimize the dominance of European colonizers over the people they were conquering.

Ethnicity refers to particular groups of people that share some common ancestry, traditions, language, or dialect. Before the world was made up of distinct nationstates or countries, certain pieces of land were associated with ethnic groups, like the Mayans or the Masai or the Celts or the Romany. Many people like to make ethnic distinctions as well as national distinctions to hold on to their ethnic culture and identity, ie 'Italian Americans' or 'African Americans'.

The word 'culture' is often misused as a euphemism for ethnicity, race, and nationality. It can be a useful term when used in a very narrow, academic sense to describe groups of people who share a language/dialect, or set of behaviors (ie 'traditions') that defines them as a specific group set apart from the dominant culture, like gay culture, or hip hop culture. And we haven't even touched upon religion at this point! But to my way of thinking, the word 'culture', as it is used nowadays, is a pretty lousy word because it causes more confusion than it clears up.

So when the original poster said "cross-cultural marriage" I asked what they meant by the word 'culture' because there is no way of knowing without asking what a person means when they say 'culture'. It might be a euphemism for race, ethnicity, nationality, straight vs gay culture, class, etc.