In wave motion, period, the time one complete cycle takes, is the reciprocal of this, the no. of cycles in a given time
[DOC] [TLE] Sound and Periodic Motion - HyperPhysics [PAR] Period: the time required to complete a full cycle, T in seconds/cycle; Frequency: 
the number of cycles per second, f in 1/seconds or Hertz (Hz); Amplitude: the ... 
from equilibrium A. and if the periodic motion is in the form of a traveling wave, 
one needs also ... time for the motion.