Translation guide
The hard protective shell covering the back of certain animals like turtles, crabs, and some insects.
The hard upper shell of a turtle or tortoise.
The hard outer covering of a crab, lobster, shrimp, or similar animal.
Also used for the shell of crabs and lobsters, though sometimes 殻 (から) is used more broadly for any hard outer covering.
The hard outer covering of insects, spiders, etc., especially the dorsal part.
Used in entomology for the dorsal sclerite of an insect or arachnid. Technical term.
甲羅 (こうら) is the most common word for turtle and crab shells in everyday language. 殻 (から) is a broader term for any hard outer covering, including eggs, nuts, and mollusks. 背甲 (はいこう) is a technical term specifically for the dorsal carapace in biology.
The turtle pulled its head into its shell.
この亀の甲羅はとても硬い。
This turtle's shell is very hard.
Specifically the carapace (upper shell) as opposed to the plastron (lower shell). More technical or biological term.
ウミガメの背甲は流線形をしている。
The sea turtle's carapace is streamlined.
カニの甲羅が脱皮して落ちていた。
The crab's shell had molted and was lying there.
General word for shell, husk, or hard outer layer. Can be used for crustaceans, but less specific than 甲羅.
エビの殻をむく。
Peel the shrimp shell.
クモの背甲には模様がある。
The spider's carapace has a pattern.
Exoskeleton; the entire external skeleton of arthropods. Broader than carapace.
昆虫は外骨格を持つ。
Insects have an exoskeleton.
Carapace or shell of crustaceans and insects; often used in compound words like 甲殻類 (crustaceans).
甲殻類の甲殻はキチン質でできている。
The shells of crustaceans are made of chitin.