Underside (noun)

The lower or under surface of something.

Origin:

From the word "under" which means below and "side" which refers to the surface of something that is facing in a particular direction.

Examples:

1. The underside of the leaf was a different color than the top.
2. She looked at the underside of the bridge as they passed under it.
3. The underside of the car was badly damaged in the accident.
4. The underside of the table was painted with a different color.
5. He looked at the underside of the mushroom before picking it.