Notch (noun)

1. A V-shaped indentation or slit in a surface or edge, especially one made to hold something.
2. A level or stage in a process or scale of values.

Origin:

From the middle english "notche" meaning "a cut or indentation".

Examples:

1. The notch on the edge of the blade was for attaching a handle.
2. He made a notch in the tree to mark his trail.
3. The notch on the belt was for adjusting the size.
4. The device had a notch to indicate the highest level.
5. He moved up a notch in the company's hierarchy.