Cardinal has several important meanings:

1. A bright red bird common in North America, with a pointed crest on its head and a strong orange beak. Male cardinals are vivid red, while females are brownish-tan with red accents. These birds don't migrate south for winter, so they stand out brilliantly against snowy landscapes. Many people enjoy watching cardinals visit their backyard bird feeders.
2. Something fundamental or of primary importance. The cardinal rule of a classroom might be to treat others with respect. When sailors discuss the cardinal directions, they mean north, south, east, and west: the four most basic directions for navigation. Scientists might talk about cardinal principles that form the foundation of their research.
3. A high-ranking official in the Catholic Church, just below the Pope. Cardinals wear distinctive red robes and help choose new Popes. When a Pope dies or resigns, the cardinals meet in Rome to elect a successor.