an abstract place usually conceived as having depth | hard outer covering or case of certain organisms such as arthropods and turtles |
a subpopulation divided into a stratified sampling | the outer layer of the skin covering the exterior body surface of vertebrates |
people having the same social, economic, or educational status | the dead skin at the base of a fingernail or toenail |
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) | |