A spectrum is a range of different but related things, often ordered from one extreme to another. In science, it especially means the band of colors produced when light is separated into its components.
From Latin *spectrum* “appearance, image, ghost,” from *specere* “to look at.” It was first used in optics to describe the colored band produced by a prism.
We took a word that once meant “ghostly appearance” and turned it into a tool for measuring everything from light to autism to political views. Whenever people say “on the spectrum,” they’re borrowing a physics idea to talk about human differences.
Complete word intelligence in one call. Free tier — 50 lookups/day.