The plural of pappus; the hair-like or feathery structure on seeds that helps them spread through the air.
From Latin pappus, from Greek pappos (grandfather, then the white downy substance). Botanists borrowed the term because the downy seed-heads resembled an old man's white beard.
Dandelion and milkweed seeds have gorgeous 'pappi' that work like tiny parachutes—NASA engineers actually study how these seed structures drift through air to design better ways to stabilize tiny spacecraft and drones.
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