What is 3-1?

3-1 can refer to several different things, depending on the context:

1. In sports, 3-1 refers to a score or series where one team or player has three wins and the other has one. For example, in a basketball game, the score might be 87-73, indicating that one team has three points for every one point the other team has. In a best-of-seven series in a sports playoff, a team that is up three games to one is said to have a "3-1 lead."

2. In mathematics, 3-1 is equivalent to 2, or the result of subtracting 1 from 3. It might also refer to a ratio of three parts to one part, or a fraction of 3/1.

3. In military terms, 3-1 can refer to a specific unit or operation. For example, the 3rd Battalion, 1st Marine Regiment is a unit in the United States Marine Corps. The term "3-1" might also be used to describe a particular mission or objective undertaken by a military unit.

Overall, the meaning of 3-1 depends on the context it is used in.