#應付機械磨損
#改變材料特性
#改變大小/形狀/質量/體積
#Manage mechanical wear
#Modify material characteristics
#Modify size/shape/mass/volume
牙齒會自行打磨銳利 (Teeth are self-sharpening)
河狸的牙齒會自行打磨銳利，因為牙齒內部的表面比外部的琺瑯質柔軟，可以更快速的磨損成鋒利的邊緣
(The teeth of beavers self-sharpen because their inner surface is softer than the outer enamel and wears away faster to create a sharp edge.)
