noun
first arrow (with left-curving feathers)
In Japanese archery (kyūdō), the first of two arrows shot in a ceremonial pair. The feathers curve to the left, causing a clockwise spin. Contrasts with 乙矢 (おとや), the second arrow with right-curving feathers.
See also: 乙矢
弓道の試合では、まず甲矢を放ち、次に乙矢を放つ。
In a kyūdō match, one first shoots the haya (first arrow), then the otoya (second arrow).
甲矢の羽は左に反っている。
The feathers of the haya curve to the left.
The second arrow in the pair, with right-curving feathers. 甲矢 is the first arrow.
The reading はや is likely related to 早 (early/first), and the kanji 甲 (first in a series) reinforces the meaning. The exact historical derivation is uncertain.