thing vs requirement

thing and requirement both are nouns.

Word	Noun	Adjective	Verb	Adverb
thing	Yes	No	No	No
requirement	Yes	No	No	No

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

thing (noun)	requirement (noun)
a separate and self-contained entity	something that is required in advance
an action	required activity
an artifact	anything indispensable
an entity that is not named specifically
any attribute or quality considered as having its own existence
a special abstraction
a special objective
a vaguely specified concern
a statement regarded as an object
an event
a persistent illogical feeling of desire or aversion
a special situation