noun

the action of departing from an established course or accepted standard.

deviation from a norm

divergence,digression,turning aside,departure,deflection,difference,variation,variance,alteration,veering,straying,fluctuation,aberration,abnormality,irregularity,anomaly,inconsistency,discrepancy,variableness,oddness,freakishness,change,shift,veer,swerve,bend,drift