(n.) Any species of South American humming birds of the genus Clytolaema. The males have a ruby-colored throat or breast.
(n.) A precious stone of a carmine red color, sometimes verging to violet or intermediate between carmine and hyacinth red. It is a red crystallized variety of corundum.
usage: "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure"