Here's a breakdown:

* Transverse wave: A wave in which the displacement of the medium is perpendicular to the direction of wave propagation. Imagine a rope tied to a wall, you shake the rope up and down, the wave travels along the rope horizontally, but the rope itself moves up and down (perpendicular).

* Crest: The highest point of a wave.

* Trough: The lowest point of a wave.

The distance between two successive crests or troughs is the wavelength, denoted by the Greek letter lambda (λ).

Here's an image to illustrate:

[Image of a transverse wave with the wavelength marked]

Important Note: Wavelength is a crucial property of waves, and it's related to the wave's frequency (how many waves pass a point per second) and the wave's speed (how fast the wave travels). The relationship is given by the equation:

Speed = Frequency x Wavelength