tablet-armed chair vs writing arm

tablet-armed chair and writing arm both are nouns.

Word	Noun	Adjective	Verb	Adverb
tablet-armed chair	Yes	No	No	No
writing arm	Yes	No	No	No

tablet-armed chair (noun)	writing arm (noun)
a chair with an arm that has been widened for writing	an arm of a tablet-armed chair; widened to provide a writing surface