A warp, curvature, or bend — the deformation or arching of a flat object (e.g., wood, metal).
木の板に反りが出て、扉がうまく閉まらない。
The wooden board warped, and the door doesn't close properly.
家具の反りを防ぐために湿度管理が重要だ。
Humidity control is important to prevent furniture from warping.
新しい床板に反りがあったので、交換してもらった。
The new floorboard was warped, so I had it replaced.
In swords (especially Japanese swords), the curvature of the blade — an aesthetic and functional characteristic.
この刀は反りが深く、切れ味に優れているとされる。
This sword has a deep curvature and is said to have excellent cutting ability.
反りの浅い刀は扱いやすく、練習刀として人気がある。
Swords with shallow curvature are easy to handle and popular as practice swords.
刀の反り具合は時代や流派で異なることが多い。
The degree of a sword's curvature often varies by period and school.