breadth
The width of something from one side to the other.
Breadth means width, or how wide something is. When you measure the breadth of your desk, you're measuring from one side to the other, not how long or tall it is. A river's breadth is how wide it stretches from bank to bank.
The word also describes range and variety. A student with breadth of knowledge understands many different topics across various subjects. Someone might have breadth in their reading habits if they enjoy mysteries, biographies, science fiction, and poetry instead of sticking to just one type of book. A museum collection has breadth when it includes art from many different time periods and cultures, not just Renaissance paintings or modern sculpture.
When people talk about the breadth of someone's experience, they mean how many different things that person has done or seen. An athlete who has played soccer, swum competitively, and run track has breadth in sports. A traveler who has visited mountains, deserts, beaches, and cities has breadth in travel.
Breadth pairs with depth: depth means how thoroughly you know something, while breadth means how widely your knowledge or experience spreads. Both matter. Sometimes you need deep expertise in one area; other times, you need broad understanding across many areas.