such as 
and 
(which might be caused at specified points by waves)
between: two oscillations with the same angular frequency such as and (which might be caused at specified points by waves)
is: a measure of the extent to which the two oscillations (or the waves causing them) are out of step. [P5.4, P6.1]
is given: by 
but is conventionally restricted to the range 
by subtracting an appropriate integer multiple of 
from 
may also be interpreted: as an angle, in which case its value is quoted in radians, or as the equivalent number of degrees. [P5.4, P6.1]
Copyright 1997, The Open University