Christmas tree vs silver fir

Christmas tree and silver fir both are nouns.

Word	Noun	Adjective	Verb	Adverb
Christmas tree	Yes	No	No	No
silver fir	Yes	No	No	No

As nouns, silver fir is a hypernym of Christmas tree; that is, silver fir is a word with a broader meaning than Christmas tree:

Christmas tree: medium to tall fir of western North America having a conic crown and branches in tiers; leaves smell of orange when crushed
silver fir: any of various true firs having leaves white or silvery white beneath

As nouns, silver fir is a hypernym of Christmas tree; that is, silver fir is a word with a broader meaning than Christmas tree:

Christmas tree: tall timber tree of central and southern Europe having a regular crown and grey bark
silver fir: any of various true firs having leaves white or silvery white beneath

Christmas tree (noun)	silver fir (noun)
an ornamented evergreen used as a Christmas decoration	any of various true firs having leaves white or silvery white beneath
medium to tall fir of western North America having a conic crown and branches in tiers; leaves smell of orange when crushed
tall timber tree of central and southern Europe having a regular crown and grey bark
a terrestrial evergreen shrub or small tree of western Australia having brilliant yellow-orange flowers; parasitic on roots of grasses
Australian tree or shrub with red flowers; often used in Christmas decoration