Tuna is a large, fast-swimming ocean fish prized for its meat. These powerful fish can weigh hundreds of pounds and swim up to 40 miles per hour, making them some of the ocean's most impressive hunters. Their streamlined bodies and strong muscles help them chase down smaller fish across vast stretches of open water.

People have fished for tuna for thousands of years. Today, tuna is one of the world's most popular fish to eat, whether grilled fresh as a steak, mixed into casseroles, or packed in cans for sandwiches. The mild-tasting meat works well in many dishes, from sushi rolls to tuna melts (a warm sandwich with melted cheese).

Different species exist: bluefin tuna can grow enormous and are prized by sushi restaurants, while smaller albacore and skipjack tuna are typically what you find canned at the grocery store. Because tuna is so popular, some species have become overfished, meaning people catch them faster than they can reproduce. When buying tuna, you might see labels like “dolphin-safe,” which means the fishing methods avoided accidentally catching dolphins that sometimes swim near tuna schools.

The word can also refer to a prickly pear cactus found in the Americas, though this meaning is much less common.