hard outer covering or case of certain organisms such as arthropods and turtles | an abstract place usually conceived as having depth |
the outer layer of the skin covering the exterior body surface of vertebrates | a subpopulation divided into a stratified sampling |
the dead skin at the base of a fingernail or toenail | people having the same social, economic, or educational status |
| one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock) |