(1)the exterior protective or supporting structure or shell of many animals (especially invertebrates) including bony or horny parts such as nails or scales or hoofs
(2)爪、うろこ、ひづめなどの骨または骨性の部分を含めた、多くの動物（特に脊椎動物）の外部の保護構造物または支持構造物