how-do-you-do vs situation

how-do-you-do and situation both are nouns.

Word	Noun	Adjective	Verb	Adverb
how-do-you-do	Yes	No	No	No
situation	Yes	No	No	No

As nouns, situation is a hypernym of how-do-you-do; that is, situation is a word with a broader meaning than how-do-you-do:

how-do-you-do (noun)	situation (noun)
an expression of greeting	a job in an organization
an awkward situation	physical position in relation to the surroundings
	the general state of things; the combination of circumstances at a given time
	a condition or position in which you find yourself
	a complex or critical or unusual difficulty