points in phase
points in a wave that have the same displacement and are moving in the same direction.
B and E
C and D

B and D are OUT of phase

wavelength
distance between two successive points in phase
BE and CD
Unit: meters or m

amplitude
maximum distance a point moves from it’s rest position
AB
Unit: meters or m

frequency
number of complete vibrations that occur in one second
Symbol: f
Unit: hertz or Hz

period
time taken for one complete vibration to occur
Symbol: T
Unit: seconds or s

wave front
line joining points in the same phase
eg: a line joining all the points on a crest of a wave

velocity
rate of change of displacement
Symbol: v
Unit: ms^-1

transverse wave
disturbance at right angles to direction of propagation of the wave

longitudinal wave
disturbance in the direction of propagation of the wave