Planetesimals

Part of speech: noun

Definitions

1. Small celestial objects originating from the solar nebula that merge as a result of gravitational forces and collisions to create larger planetary formations
2. Tiny remnants of dust and ice that accumulate within protoplanetary discs, leading to the development of larger celestial bodies, including planets
3. Small rocky or icy objects in the early solar system that grow by colliding and sticking together to eventually form planets

Etymology: The plural form simply takes the regular "-s" of its singular, "planetesimal", so the real story is in the singular. It was coined by analogy with "infinitesimal", a word meaning infinitely small, which was built on the Latin "infinitus" ("unbounded") and the adjective-forming suffix "-esimal". The pattern produced a new term meaning "small planet", a label for the tiny bodies imagined as the building blocks of larger worlds. The "planet" element comes from Greek "planētēs", "wanderer", because ancient observers saw these bright points moving against the fixed stars. Coined by analogy with a word for the infinitely small, the term turned that old idea of wandering into a description of the tiny bodies that gather into worlds.