A filament is a very thin thread or wire, especially one that glows inside a light bulb. It can also mean any slender strand in plants, animals, or materials.
It comes from Latin “filamentum,” from “filum,” meaning “thread.” The word has long been used for fine, thread-like structures.
The glowing wire in old light bulbs is literally a bright thread, matching the word’s root. Even in biology and 3D printing, we still call long, thin strands “filaments,” showing how a simple thread idea stretches across many fields.
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