WordNet records no synonym and no antonym for chalaza. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
basal part of a plant ovule opposite the micropyle; where integument and nucellus are joined
one of two spiral bands of tissue connecting the egg yolk to the enclosing membrane at either end of the shell
Synonyms, antonyms and the broader and narrower relations for chalaza come from Princeton University’s WordNet. Full sources and licences.