lymph gland vs bubo

lymph gland and bubo both are nouns.

Word	Noun	Adjective	Verb	Adverb
lymph gland	Yes	No	No	No
bubo	Yes	No	No	No

As nouns, bubo is a hyponym of lymph gland; that is, bubo is a word with a more specific, narrower meaning than lymph gland:

lymph gland: the source of lymph and lymphocytes
bubo: a lymph node that is inflamed and swollen because of plague or gonorrhea or tuberculosis

Other hyponyms of lymph gland include axillary node, Peter's gland, Peyer's patch.

lymph gland (noun)	bubo (noun)
the source of lymph and lymphocytes	a lymph node that is inflamed and swollen because of plague or gonorrhea or tuberculosis