Margin (noun)

1. A blank space around the edge of a printed page.
2. An amount by which a sum of money exceeds what is needed.
3. A limit or boundary beyond which a thing cannot or is unlikely to go.

Origin:

Late middle english: from latin margo "edge, border".

Examples:

1. She added a note in the margin of the book.
2. There is a small margin of error in these calculations.
3. The margin of victory in the election was less than one percent.
4. The company operates on a slim margin.
5. He tries to maintain a wide margin of safety in his investments.