Keratinous
角朊的, 角質的, 角(質)蛋白的
??? 情景例句
As a matter of fact,
事實上，
In every rank, great or small, 'Tis industry supports us all.
不論高的低的各級人士，所持的都是勤勞。
a trough (the lowest point), a height (the vertical distance from the trough to the crest),
波谷（最低點）、浪高（從波谷到浪峰的垂直距離）