thallus vs plant part

thallus and plant part both are nouns.

Word	Noun	Adjective	Verb	Adverb
thallus	Yes	No	No	No
plant part	Yes	No	No	No

As nouns, plant part is a hypernym of thallus; that is, plant part is a word with a broader meaning than thallus:

thallus: a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes
plant part: any part of a plant or fungus

Other hypernyms of thallus include plant structure.

thallus (noun)	plant part (noun)
a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes	any part of a plant or fungus