emphasis vs word stress

emphasis and word stress both are nouns.

Word	Noun	Adjective	Verb	Adverb
emphasis	Yes	No	No	No
word stress	Yes	No	No	No

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

emphasis: the relative prominence of a syllable or musical note (especially with regard to stress or pitch)
word stress: the distribution of stresses within a polysyllabic word

Other hyponyms of emphasis include accentuation, pitch accent, tonic accent, word accent, sentence stress.

emphasis (noun)	word stress (noun)
intensity or forcefulness of expression	the distribution of stresses within a polysyllabic word
the relative prominence of a syllable or musical note (especially with regard to stress or pitch)
special and significant stress by means of position or repetition e.g.
special importance or significance