Negligible refers to the quantities so small that they can be ignored (neglected) when studying the larger effect. Although related to the more mathematical concepts of infinitesimal, the idea of negligibility is particularly useful in practical disciplines like physics, chemistry, mechanical and electronic engineering, computer programming and in everyday decision-making. A quantity can be said to be negligible when it is safe to ignore (neglect) it in the present case, within the margins for error that have been agreed to be acceptable in this case. Examples of quantities that are often considered negligible are the electrical resistance of a wire, and the mass of the electrons in an atom.