An anomaly is a deviation from the common rule. It is an irregularity that is difficult to explain using existing rules or theory.

• In astronomy, the anomaly is the angular distance of a planet from its periapsis:
  • The true anomaly is observed from the primary (I.e., from the orbit's focus.);
  • The eccentric anomaly is observed from the centre of the ellipse, using a projection of the planet's position onto the circumscribing circle; and
  • The mean anomaly is the fraction of an orbital period that has elapsed, expressed as an angle.
• In an anomaly time series the times are not uniformly spaced.
• In physics, an anomaly is a classical symmetry that is not a symmetry of the quantum theory. See anomaly (physics).
• Anomaly is a metal band in Malta. See Anomaly (band). [1]
• Anomaly is a four piece punk/rock band from Tasmania, Australia.