epithelium vs decidua

epithelium and decidua both are nouns.

Word	Noun	Adjective	Verb	Adverb
epithelium	Yes	No	No	No
decidua	Yes	No	No	No

As nouns, decidua is a hyponym of epithelium; that is, decidua is a word with a more specific, narrower meaning than epithelium:

epithelium: membranous tissue covering internal organs and other internal surfaces of the body
decidua: the epithelial tissue of the endometrium

Other hyponyms of epithelium include endothelium, mesothelium, neuroepithelium.

epithelium (noun)	decidua (noun)
membranous tissue covering internal organs and other internal surfaces of the body	the epithelial tissue of the endometrium