margin

Noun

(countable) A margin is the space on the sides of a page where there is no writing.
If you own the book, write notes in the margin.
(countable) A margin is the difference between what the winner has and what the loser has.
The team won every game with an average 24-point victory margin per game.

The Board of Education voted by a narrow margin to accept the new standards.

Mitt Romney is leading in the latest polls by a slim margin, 29 percent of the vote to John McCain's 26 percent.
(countable) A margin is the difference between what a business pays for something and what it sells it for.
The current profit margins on those products run between 55 and 62 percent.
(countable) A margin is extra time, room, money, etc. that you plan for in case something needs more.
There's almost no margin for error with the landing the plane.

The extra fuel that was carried along gave us a bit of a safety margin.
(countable) A margin of error is the amount that the true value varies from the measured value.
The poll had a margin of error of plus or minus 4 percentage points.

We produce these pieced to be 2.5 meters long, with an overall error margin of 1.4 millimeters.
If somebody is on the margin(s), they are not a central member and have little power.