A navy is a nation's military force that operates at sea. While an army fights on land and an air force flies planes, the navy protects a country's interests on and under the ocean using warships, submarines, and aircraft carriers.

Throughout history, powerful navies have shaped the world. The British Navy once dominated the seas, helping Britain build a global empire. The United States Navy today patrols oceans worldwide, protecting shipping lanes and responding to crises. Naval battles like Midway in World War II changed the course of history.

A modern navy does more than fight. Navy ships rescue people in disasters, deliver humanitarian aid, and conduct scientific research. Submarines patrol silently underwater. Aircraft carriers serve as floating airbases, launching jets thousands of miles from home.

The word navy also refers to a dark blue color, called navy blue, because it matches the traditional color of naval uniforms. When someone says they're wearing navy pants, they mean dark blue ones.

People who serve in the navy are called sailors or naval officers. Joining the navy means training to work as part of a crew, where everyone depends on one another while living aboard a ship for months at sea.