subcontinent vs land mass

subcontinent and land mass both are nouns.

Word	Noun	Adjective	Verb	Adverb
subcontinent	Yes	No	No	No
land mass	Yes	No	No	No

As nouns, land mass is a hypernym of subcontinent; that is, land mass is a word with a broader meaning than subcontinent:

subcontinent: a large and distinctive landmass (as India or Greenland) that is a distinct part of some continent
land mass: a large continuous extent of land

Other hypernyms of subcontinent include landmass.

subcontinent (noun)	land mass (noun)
a large and distinctive landmass (as India or Greenland) that is a distinct part of some continent	a large continuous extent of land