cortex vs renal cortex

cortex and renal cortex both are nouns.

Word	Noun	Adjective	Verb	Adverb
cortex	Yes	No	No	No
renal cortex	Yes	No	No	No

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

cortex: the tissue forming the outer layer of an organ or structure in plant or animal
renal cortex: the cortex of the kidney containing the glomeruli and the convoluted tubules

Other hyponyms of cortex include adrenal cortex.

cortex (noun)	renal cortex (noun)
the tissue forming the outer layer of an organ or structure in plant or animal	the cortex of the kidney containing the glomeruli and the convoluted tubules
the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
the tissue that surrounds the lens nucleus