Mesofact

A fact or truth or opinion that evolves very slowly, to the point where you don’t notice that it’s changed over a period of time.

This is not a traditional word. I think it was invented about a decade ago, first in this Boston Globe article: Warning: Your reality is out of date

When people think of knowledge, they generally think of two sorts of facts: facts that don’t change, like the height of Mount Everest or the capital of the United States, and facts that fluctuate constantly, like the temperature or the stock market close.

But in between there is a third kind: facts that change slowly. These are facts which we tend to view as fixed, but which shift over the course of a lifetime.

“mesa” is a Greek prefix for “middle,” which is the idea of the word: some things change quickly, some never change, but things in the “meso” change slowly.

I’ve seen the word many times in the 10 years since, so I think it’s achieved some level of adoption.

Some of the mesofacts mentioned in the article and in other places:

• What percentage of people in the world who use mobile phones?
• What the the population of the Earth?
• How many planets are outside the solar system?
• Should you gargle with mouthwash?

Some of these change because they’re naturally fluid (the population question, for example), while other change because new information and research appears and is slowly accepted over time.