absolute

1. With respect to atmospheric motions, refers to an absolute coordinate system; for example, absolute vorticity as distinguished from relative vorticity.
2. In climatology, the highest or lowest recorded value of a meteorological element, whether at a single station or over an area, during a given period.
   It is most frequently applied to extremes of temperature: absolute maximum is the highest recorded shade temperature; absolute minimum is the lowest recorded.
   
3. 
   See Kelvin temperature scale.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.