stiff vs inflexible

stiff is a noun but inflexible is not a noun.

Word	Noun	Adjective	Verb	Adverb
stiff	Yes	Yes	No	Yes
inflexible	No	Yes	No	No

stiff (noun)	inflexible (noun)
the dead body of a human being
an ordinary man

stiff (adjective)	inflexible (adjective)
having a strong physiological or chemical effect	resistant to being bent
rigidly formal	incapable of change
not moving or operating freely	not making concessions
very drunk	incapable of adapting or changing to meet circumstances
marked by firm determination or resolution; not shakable
strong, vigorous
incapable of or resistant to bending

stiff (adverb)	inflexible (adverb)
in a stiff manner
to a great degree