noun, noun or participle which takes 'suru'
Archaic noun and suru-verb meaning gradual loss of strength, vitality, or prosperity. Not used in modern Japanese; replaced by 衰退 (すいたい) or 衰え (おとろえ).
古典では、国力の衰替を嘆く表現が見られる。
In classical texts, one finds expressions lamenting the decline of national strength.
Compound of 衰 (decline) and 替 (change/replace), suggesting a shift toward weakness. The exact historical derivation is uncertain; the word is now obsolete.