Usually, age is determined by physical characteristics, such as teeth or bones.

通常说来，年龄是通过生理特征确定的，譬如牙齿或骨骼。

youdao

A protective covering, structure, or organ of an animal or a plant, such as teeth, claws, thorns, or the shell of a turtle.

防御器官动物或植物的防护层，结构或器官，如牙齿，爪子，荆棘或乌龟的壳。

youdao

It had feathers and other traits of living birds but also vestiges of a reptilian past, such as teeth in its mouth, claws on its wings, and a long, bony tail.

始祖鸟拥有羽毛，它身上既有现代鸟类的特征，也有远古爬行动物的痕迹，例如口中有牙齿，翅膀上有爪子，还有一条硕长的骨质尾巴。

youdao

In April 2010 Chestnut was sued by a former investor who alleged fraud and accused Plummer of using investors' money for such things as porcelain teeth veneers, a Lexus SUV for his wife and membership at Dallas' Canyon Creek Country Club.

FORBES: Magazine Article

With the comfort of permanent agricultural settlements came uncomfortable new scourges such as intestinal parasites, bad teeth and the fouling of the water supply.

ECONOMIST: Food in history

Other harsh ceremonies, such as circumcision without anesthetic, teeth sharpening, and physical disfiguration, make what I suggest individual investors endure seem like a tiptoe through the tulips by comparison.

FORBES: Investor Rites of Passage - Part 1