WordNet records no synonym and no antonym for modulus. 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.
an integer that can be divided without remainder into the difference between two other integers
“2 is a modulus of 5 and 9”
the absolute value of a complex number
(physics) a coefficient that expresses how much of a specified property is possessed by a specified substance
Synonyms, antonyms and the broader and narrower relations for modulus come from Princeton University’s WordNet. Full sources and licences.