What do secret societies, infectious diseases, and male dominance hierarchies have in common? They all make use of a symbol system that was first developed over 2,500 years ago. Since that time, it has been continually repurposed in all sorts of surprising ways. There may be no set of characters as widely deployed—or as adaptable—as the letters of the Greek alphabet.

This symbol system was standardized as a set of 24 letters—from alpha to omega—during the 4th century BC. Because a knowledge of ancient Greek was widely shared by members of Europe’s educated class, Greek letters were readily pressed into service for other purposes. Over time, they found employment as mathematical constants—such as pi (π)—and as variables in fields like engineering and physics.

A very different application for Greek letters arose in early America. In December of 1776, a secret literary and philosophical society was established at Virginia’s College of William and Mary. Its organizers named it using the Greek-letter initialism of ΦΒΚ—Phi Beta Kappa—from the first letters of Philosophia Biou Kybernētēs, or “philosophy [is the] guide of life.”

Today, about 1,500 Greek letter fraternities and sororities can be found on hundreds of campuses across North America. The number of college students involved in panhellenic activities is estimated to be in the hundreds of thousands.

During the Covid pandemic, researchers used Greek letters to identify new variants of the........

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