Coral is made up of small colonial animals, with calcium carbonate skeletons.
珊瑚是由小型珊瑚虫及其碳酸钙骨骼聚集而成的。
英语百科
Colony (biology)
In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another, usually for mutual benefit such as stronger defense or the ability to attack bigger prey. In contrast, a solitary organism is one in which all individuals live independently and have all of the functions needed to survive and reproduce.