third tonsil vs lymphoid tissue

third tonsil and lymphoid tissue both are nouns.

Word	Noun	Adjective	Verb	Adverb
third tonsil	Yes	No	No	No
lymphoid tissue	Yes	No	No	No

As nouns, lymphoid tissue is a hypernym of third tonsil; that is, lymphoid tissue is a word with a broader meaning than third tonsil:

third tonsil: a collection of lymphatic tissue in the throat behind the uvula (on the posterior wall and roof of the nasopharynx)
lymphoid tissue: tissue making up the lymphatic system

Other hypernyms of third tonsil include lymphatic tissue.

third tonsil (noun)	lymphoid tissue (noun)
a collection of lymphatic tissue in the throat behind the uvula (on the posterior wall and roof of the nasopharynx)	tissue making up the lymphatic system