thing vs must-see

thing and must-see both are nouns.

Word	Noun	Adjective	Verb	Adverb
thing	Yes	No	No	No
must-see	Yes	No	No	No

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

thing (noun)	must-see (noun)
a separate and self-contained entity	something which is considered required to see
an action
an artifact
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