Sea is a large body of salt water, usually part of an ocean or connected to one. The Mediterranean Sea, Caribbean Sea, and South China Sea are all enormous areas of ocean water with their own names, often partly enclosed by land. Sailors and explorers have crossed these seas for thousands of years, connecting distant civilizations.

When people talk about going to the sea, they usually mean the ocean or coast, where waves crash on beaches and salt spray fills the air. The phrase out to sea means away from land, into open water. A sea voyage is a journey across ocean waters, like the Atlantic crossings that brought European settlers to the Americas.

The word also describes anything having to do with ocean water: sea lions and sea turtles live in the ocean, sea salt comes from evaporated ocean water, and sea level is the height of the ocean's surface, which scientists use as a reference point for measuring elevation on land.

Sometimes sea describes any huge expanse: a wheat field stretching to the horizon might look like a sea of golden grain, and a crowded auditorium might contain a sea of faces. These expressions capture that same feeling of vastness you get looking across endless ocean water.