streambed vs dry wash

streambed and dry wash both are nouns.

Word	Noun	Adjective	Verb	Adverb
streambed	Yes	No	No	No
dry wash	Yes	No	No	No

As nouns, dry wash is a hyponym of streambed; that is, dry wash is a word with a more specific, narrower meaning than streambed:

streambed: a channel occupied (or formerly occupied) by a stream
dry wash: the dry bed of an intermittent stream (as at the bottom of a canyon)

Other hyponyms of streambed include wash.

streambed (noun)	dry wash (noun)
a channel occupied (or formerly occupied) by a stream	the dry bed of an intermittent stream (as at the bottom of a canyon)