nervure vs midvein

nervure and midvein both are nouns.

Word	Noun	Adjective	Verb	Adverb
nervure	Yes	No	No	No
midvein	Yes	No	No	No

As nouns, midvein is a hyponym of nervure; that is, midvein is a word with a more specific, narrower meaning than nervure:

nervure: any of the vascular bundles or ribs that form the branching framework of conducting and supporting tissues in a leaf or other plant organ
midvein: the vein in the center of a leaf

Other hyponyms of nervure include midrib.

nervure (noun)	midvein (noun)
one of the horny ribs that stiffen and support the wing of an insect	the vein in the center of a leaf
any of the vascular bundles or ribs that form the branching framework of conducting and supporting tissues in a leaf or other plant organ