Valley and Wadi

Valley noun - An area of lowland between hills or mountains.

Wadi and valley are semantically related. In some cases you can use "Wadi" instead a noun "Valley".

Wadi noun - Gully or streambed in northern Africa and the Middle East that remains dry except during rainy season.

Valley and wadi are semantically related. Sometimes you can replace term "Valley" with "Wadi", this nouns are similar.