stiffener vs structural member

stiffener and structural member both are nouns.

Word	Noun	Adjective	Verb	Adverb
stiffener	Yes	No	No	No
structural member	Yes	No	No	No

As nouns, structural member is a hypernym of stiffener; that is, structural member is a word with a broader meaning than stiffener:

stiffener: a member attached to a beam web to prevent loss of strength due to web buckling.
structural member: support that is a constituent part of any structure or building

stiffener (noun)	structural member (noun)
a member attached to a beam web to prevent loss of strength due to web buckling.	support that is a constituent part of any structure or building
material used for stiffening something