Call it the crisis of whiteness.

White anxiety has fueled this year’s political tumult in the West: Britain’s surprising vote to exit the European Union, Donald J. Trump’s unexpected capture of the Republican presidential nomination in the United States, the rise of right-wing nationalism in Norway, Hungary, Austria and Greece.

Whiteness, in this context, is more than just skin color. You could define it as membership in the “ethno-national majority,” but that’s a mouthful. What it really means is the privilege of not being defined as “other.”

Whiteness means being part of the group whose appearance, traditions, religion and even food are the default norm. It’s being a person who, by unspoken rules, was long entitled as part of “us” instead of “them.”

But national and racial identity were often conflated for the white majority. That identity felt to many white people like one of the most important pillars holding up their world — and now it seems under threat.