cortex has 4 distinct synonyms spread across 2 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is medulla.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
Synonyms, antonyms and the broader and narrower relations for cortex come from Princeton University’s WordNet. Full sources and licences.
the tissue forming the outer layer of an organ or structure in plant or animal