altimeter vs hypsometer

altimeter and hypsometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
altimeter	Yes	No	No	No
hypsometer	Yes	No	No	No

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

altimeter: an instrument that measures the height above ground; used in navigation
hypsometer: an altimeter that uses the boiling point of water to determine land elevation

altimeter (noun)	hypsometer (noun)
an instrument that measures the height above ground; used in navigation	an altimeter that uses the boiling point of water to determine land elevation