silk cotton vs plant fibre

silk cotton and plant fibre both are nouns.

Word	Noun	Adjective	Verb	Adverb
silk cotton	Yes	No	No	No
plant fibre	Yes	No	No	No

As nouns, plant fibre is a hypernym of silk cotton; that is, plant fibre is a word with a broader meaning than silk cotton:

silk cotton: a plant fiber from the kapok tree; used for stuffing and insulation
plant fibre: fiber derived from plants

Other hypernyms of silk cotton include plant fiber.

silk cotton (noun)	plant fibre (noun)
a plant fiber from the kapok tree; used for stuffing and insulation	fiber derived from plants