1. There were many baseball players on the baseball field.

2. There were many baseball players on the baseball stadium.

3. There were many baseball players on the ball park.
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Which expressions can we use for the place where baseball games are played?
Which ones are commonly used?

One (or many) is/are not ON a stadium or a ballpark. Is someone sitting or standing on the roof? Players are on the field, not the roof.

The expressions commonly used to refer to the place where baseball games are played are "baseball field" and "ball park." Both of these expressions are commonly used and easily understood by most people.

"Baseball field" is a broad term that can refer to any playing area specifically designated for baseball. It typically includes the infield, outfield, and any necessary markings or structures such as bases, foul lines, and dugouts. This term is widely used and understood by both casual fans and baseball enthusiasts.

"Ball park" is another commonly used term for the place where baseball games are played. It is more informal and is often used to describe a stadium or sports complex specifically built for baseball. While it can refer to any baseball venue, it is commonly associated with larger stadiums that host professional or major league games. The term "ball park" is often used in a figurative sense to describe the overall atmosphere or location of a baseball game.

On the other hand, "baseball stadium" is also a valid expression to describe the place where baseball games are played, but it is not as commonly used as "baseball field" or "ball park." "Baseball stadium" typically refers to a larger and more substantial venue specifically constructed for baseball events. It often implies a professional or semi-professional level of competition. However, it is worth mentioning that the term "stadium" can also be used more generally to refer to any large sports facility or arena, regardless of the specific sport being played.

In summary, the commonly used expressions for the place where baseball games are played are "baseball field" and "ball park." "Baseball stadium" is also a valid term, although it is less commonly used.