length vs wingspread

length and wingspread both are nouns.

Word	Noun	Adjective	Verb	Adverb
length	Yes	No	No	No
wingspread	Yes	No	No	No

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

Other hyponyms of length include leg, arm's length, gauge, light time, skip distance, wingspan, altitude.

length (noun)	wingspread (noun)
a section of something that is long and narrow	distance between the tips of the wings (as of a bird or insect) when fully extended
the linear extent in space from one end to the other; the longest dimension of something that is fixed in place	linear distance between the extremities of an airfoil
continuance in time
the property of being the extent of something from beginning to end
size of the gap between two places