Complex

n.
  1. Assemblage of related things; collection; complication.
    2. Complex of lines (Geom.),
    all the possible straight lines in space being considered, the entire system of lines which satisfy a single relation constitute a complex; as, all the lines which meet a given curve make up a complex. The lines which satisfy two relations constitute a congruency of lines; as, the entire system of lines, each one of which meets two given surfaces, is a congruency.