yearbook vs ephemeris

yearbook and ephemeris both are nouns.

Word	Noun	Adjective	Verb	Adverb
yearbook	Yes	No	No	No
ephemeris	Yes	No	No	No

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

yearbook: a reference book that is published regularly once every year
ephemeris: an annual publication containing astronomical tables that give the positions of the celestial bodies throughout the year

Other hyponyms of yearbook include almanac, almanac, farmer's calendar.

yearbook (noun)	ephemeris (noun)
a reference book that is published regularly once every year	an annual publication containing astronomical tables that give the positions of the celestial bodies throughout the year
a book published annually by the graduating class of a high school or college usually containing photographs of faculty and graduating students