Basement (noun)

The lowermost portion of a building, partly or wholly below ground level; often used for storage.

Origin:

Late 16th century (in the sense "ground floor of a building"): from base + -ment.

Examples:

1. The basement was damp and musty.
2. The basement of the old house was filled with old furniture and boxes.
3. I found an old painting in the basement of my grandparents' house.
4. The basement had a small window that let in very little light.
5. I decided to turn the basement into a game room.