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pair

Things taken by two's, either two matching objects (a pair of gloves, a pair of lovers) or a single object clearly composed of two matching parts (a pair of scissors, a pair of trousers). However, there are some interesting exceptions, mostly British regional:

From the tin mines of east Cornwall, at least as early as the 18ᵗʰ – 19ᵗʰ century, and in Australia:
pair, a set of miners that work together in a gang.

pair of moyles (mules), usually about thirty, for carrying tin.

M. A. Courtney.
West Cornwall.
in Glossary of Words in Use in Cornwall.
Published for the English Dialect Society.
London: Trübner and Company, 1880.
Widespread, at least as early as the 16ᵗʰ century: “a pair of cards”, meaning a deck or pack of playing cards.
In presentation to the British monarch by the Royal Society of Archers, “a pair of arrows” is 3 arrows.