A group of cottages or a small settlement of humble dwellings, or in algebra, a subset generated by multiplying elements of a group by a fixed element.
From 'cot' (cottage) + 'set' (collection), or from mathematical terminology. The mathematical sense dates to 20th-century algebra.
It's wild that the same word describes both a village arrangement and an abstract mathematical concept—it shows how 'set' became the lingua franca of modern math, replacing words like 'aggregate' or 'collection.'
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