• 貝かい — shell; shellfish
• 貝類かいるい — shellfish category
• 貝細工かいざいく — shell craft
• 巻貝まきがい — spiral shell
• 赤貝あかがい — ark shell
• 貝殻かいがら — seashell

“貝” originally represented a cowrie shell, which was widely used as money in ancient times. Because of this, 貝 appears in many kanji related to value, cost, and exchange — such as 買 (buy), 費 (expense), and 賞 (reward).