plural of 'hair': individual thin strands that grow from the skin (on the head or body) or separate fibers from an animal or object.

『hair』の複数形：皮膚（頭や体）や動物・物から生える細い1本1本の毛（細い繊維）

small amounts or tiny distances when used in set phrases (e.g., 'a hair's breadth'); refers to very small degree or margin.

決まり文句で使われるときのごく小さな量・ごくわずかな差（例：a hair's breadth）