* A small, enclosed area for keeping animals, especially pigs or sheep: "The farmer kept his pigs in a pen."
* A fenced-in area, especially for sports: "The soccer team practiced in the pen at the back of the field."
* A group of writers or journalists: "The literary pen was full of talented authors."
* A place where something is kept or stored: "He keeps his collection of rare books in a special pen."
It's important to consider the context to understand which meaning of "pen" is intended.