Plural of quad; either quadriceps leg muscles, or open courtyards surrounded by buildings (common on college campuses).
Short for 'quadriceps' (four muscles) or 'quadrangle' (four-sided courtyard). Both shortened forms became popular in the 1900s.
College quads were originally designed by medieval monasteries as peaceful spaces for learning, and they're so psychologically effective that universities still build them even though it's expensive compared to other designs.
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