Merriam-Webster’s Collegiate Dictionary defines “xenophobia” as “fear and hatred of strangers or foreigners or of anything that is strange or foreign.”

The American Heritage Dictionary agrees but adds the emphasis on “different countries or cultures”: “Fear of, hatred of, mistrust of, or contempt for that which is foreign, especially strangers or people from different countries or cultures.”

Something about the word, and all the other -phobias, raises the specter of frothing-at-the-mouth hatred, the kind seen at Trump rallies, cross-burnings, and the “Unite the Right” march last August in Charlottesville, Virginia, where swastikas and other Nazi regalia were much in evidence. Connecting “xenophobia” to Martha’s Vineyard, my own first thought was of the contempt directed by some U.S.-born Vineyarders to the Brazilian population, especially the undocumented members of it.

Then I considered the blatant homophobia I encountered on the Vineyard in the early 1990s, in person and in print, which did much to inspire The Mud of the Place. Some of its manifestations came close to that frothing-at-the-mouth specter, but what was more unsettling was the reluctance of so many liberal types to take it seriously and speak out publicly against it.

Blogging “I is for Islander” had me thinking yet again of all the ways we divide people into Us and Them, not by their personal characteristics but by the groups they belong to. We don’t froth at the mouth when we do this, but some audible animosity is often in evidence. Off the top of my head, here are some of the categories I hear most often. A few of them occupy considerable space in my own head.

• Summer people
• Wash-ashores
• Native islanders
• Landlords
• Tenants
• Republicans
• Liberals
• New Yorkers
• Millennials
• Immigrants

Does fear, hatred, and resentment of any of these groups amount to xenophobia? Generally, no, as long as we equate “xenophobia” with that frothing-at-the-mouth hatred seen at alt-right rallies.

But let’s not let ourselves off the hook so easily.

“Xenophobia” is what I like to call an envelope word. We stuff a bunch of related observations and insights into an envelope, seal it, and gradually forget how complex and even occasionally contradictory its contents are. Xenophobia gradually morphs from description into explanation, and since it’s generally seen as a bad thing, we devote considerable effort to defending ourselves against any suggestion that we might be somewhat xenophobic.

Or racist, sexist, or any of a host of other unpleasant, corrosive, but persistent characteristics.

It’s not hard to find one or two or five or even fifty bad apples among any of the above categories. It’s also easy for those bad apples to become the rule and everyone else the exception, even if the exceptions far outnumber those who fit the rule — especially when you’re surrounded by people who think the same way.

And in a society with serious and growing income and wealth inequality, resentment isn’t hard to understand. The huge problem is that it’s usually directed at safe targets. This is one hell of a lot easier than identifying and addressing the underlying causes — which not infrequently include people we like, and maybe even our own selves.