• Returns union of given sets
• Sets are lists composed of any kind of data
• Given sets may be specified either by a variable containing two or more lists or by sets named within parentheses

Example:
  (UNION-OF ((COMMON-ORTHOLOGS-OF (Npun A7120))
             (COMMON-ORTHOLOGS-OF (Npun Avar))))
  :: 3894 common orthologs found
     2131 common orthologs found
     4288 elements in INTERSECTION
     (#$Npun.p-pNPBF129 #$Npun.p-pNPDR020 #$Npun.p-NpR2013 #$Npun.p-pNPAR273
      #$Npun.p-pNPBF152 #$Npun.p-NpR6153 #$Npun.p-NpR6290 #$Npun.p-pNPCF077
      ...

[Result is a list of proteins from N. punctiforme found also in either Anabaena PCC 7120
or Anabaena variabilis]