A gulf is a large area of ocean or sea that extends deep into the land, larger than a bay but smaller than an actual sea. The Gulf of Mexico, for instance, is a huge body of water bordered by the United States, Mexico, and Cuba. The Persian Gulf sits between Iran and the Arabian Peninsula. These gulfs are important for shipping, fishing, and trade because they give ships sheltered water routes far inland.

The word also describes a wide separation or difference between people, ideas, or situations. When there's a gulf between two friends' opinions on something important, they seem very far apart in their thinking. Teachers might talk about closing the gulf between struggling students and advanced ones. A vast gulf suggests an enormous distance: a gap so wide it seems almost impossible to bridge.

You might notice that both meanings share the idea of distance or separation. Just as a physical gulf creates space between shores, a metaphorical gulf creates space between people or ideas. When someone says “there's a real gulf between us on this issue,” they mean the disagreement feels as wide and deep as a real gulf.