1 occurrence: single 2 occurrences: double 3 occurrences: triple 4 occurrences: quadruple 5 occurrences: quintuple Single, double, and triple are the only ones that are very commonly used. You may occasionally see quadruple or quintuple. If you are talking about groups of people or items (perhaps singing groups, for example), here is the series: 1) solo 2) duo 3) trio 4) quartet 5) quintet 6) sextet 7) septet 8) octet

4 -> quadruple 5 -> quintuple 6 -> sextuple The list goes on, you can find more here: http://en.wikipedia.org/wiki/4-tuple#Names_for_tuples_of_specific_lengths