Vergences

Part of speech: noun

Definitions

1. The act or process of converging, where multiple lines or paths meet at a single point
2. A merging or coming together of different perspectives or ideas
3. A phenomenon in optics where rays of light come together at a focal point

Etymology: Vergence is a technical coinage, and its most surprising feature is that it was built to be a umbrella term. Ophthalmologists needed a single word covering both the bending of light rays toward one point and their spreading apart, so in 1902 they took "verge," meaning to tend or incline, and added the suffix "-ence." The result works as a hypernym: convergence and divergence are both kinds of vergence. The word is not an ancient one. The idea of a earlier English "vergency," dating from the 1660s, had already existed as the equivalent of the French "vergence," but the 1902 ophthalmic sense is what gave the modern form its current shape. The "verge" at its root comes from Latin "vergere," meaning to bend or turn toward. In the 1920s the term moved into geometric optics, where it became a numeric quantity describing how strongly light rays converge or diverge. Plural "vergences" simply refers to several such measurements or instances of the phenomenon.