Plural of achene; small, dry, single-seeded fruits that don't open to release seeds, like the seeds of sunflowers and dandelions.
From Greek 'a-' (not) plus 'chainein' (to gape or open), because these fruits don't split open like pods, a botanical term coined to describe this specific fruit type.
Achenes are sneaky seed packets—they look like simple seeds but are actually whole fruits, and plants spread them by making them feathery or sticky so they hitchhike on wind and animals.
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