deviation >> /ˌdiviˈeɪʃ(ə)n/
Definition: [noun] The action of departing from an established course or accepted standard.
Example: deviation from a norm
Definition: [noun] The amount by which a single measurement differs from a fixed value such as the mean.
Example: a significant deviation from the average value
Definition: [noun] The deflection of a vessel's compass needle caused by iron in the vessel, which varies with the vessel's heading.
Example: In 1819 Barlow began work on the problem of deviation in ship compasses caused by the presence of iron in the hull.