cardinal
adjective
°Of fundamental importance; crucial, pivotal.
"a cardinal rule"
°(nautical) Of or relating to the cardinal directions (north, south, east and west).
"a cardinal mark"
noun
°A number indicating quantity, or the size of a set, e.g., one, two, three. (See Wikipedia article on Cardinal number.).
°An official in the Catholic Church, ranking only below the Pope and the patriarchs. (See .).