quartet quartet /kwɔrˈtɛt/

noun

1. A musical composition for four performers  ( quartet , quartette )
   a musical composition for four performers
   
2. Four people considered as a unit  ( quartet , quartette , foursome )
   four people considered as a unit
    He joined a barbershop quartet
   he joined a barbershop quartet
    The foursome teed off before 9 a.m.
   the foursome teed off before 9 a.m.
   
3. A set of four similar things considered as a unit  ( quadruple , quadruplet , quartet , quartette )
   a set of four similar things considered as a unit
   
   
4. Four performers or singers who perform together  ( quartet , quartette )
   four performers or singers who perform together
   
5. The cardinal number that is the sum of three and one  ( foursome , IV , Little Joe , quadruplet , quartet , quatern , quaternary , quaternion , quaternity , 4 , four , tetrad )
   the cardinal number that is the sum of three and one
    I have four books to read for my class
   I have four books to read for my class