The verb to sink means to drop below the surface of water or another liquid and disappear from view. When a stone sinks in a pond, it falls through the water until it rests on the bottom. Ships sink when they take on too much water and can no longer stay afloat. The Titanic famously sank after hitting an iceberg in 1912, settling on the ocean floor where it remains today.

Things sink because they're denser than water, meaning they're heavier than the same amount of water would be. A metal spoon sinks, but a wooden spoon floats. This is why ships, even though they're made of heavy steel, can float: their hulls contain air, making them less dense overall than water. But once that air space fills with water, down they go.

The word also describes gradually moving downward in other contexts. The sun sinks below the horizon at sunset. Your heart might sink when you hear disappointing news, meaning you suddenly feel deflated or sad. When you feel yourself sinking into a comfortable chair, you're settling deeper into it. If someone says “that lesson really sank in,” they mean they finally understood it deeply.

A sink is also the basin in your kitchen or bathroom where you wash your hands and dishes, with a drain at the bottom where water disappears, almost like it's sinking away.