Nouns

(n)four, 4, IV, tetrad, quatern, quaternion, quaternary, quaternity, quartet, quadruplet, foursome, Little Joethe cardinal number that is the sum of three and one
(n)quartet, quartettefour performers or singers who perform together
(n)quartet, quartette, quadruplet, quadruplea set of four similar things considered as a unit
(n)quartet, quartette, foursomefour people considered as a unit“he joined a barbershop quartet”, “the foursome teed off before 9 a.m.”
(n)quartet, quartettea musical composition for four performers