wave ‧ length /ˈweɪvleŋθ/ BrE AmE noun [countable]
1 . the size of a radio wave used to broadcast a radio signal
2 . technical the distance between two points on energy waves such as sound or light
3 . be on the same/a different wavelength informal to have the same or different opinions and feelings as someone else:
Dad is just on a different wavelength from me.