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isologue

American  
[ahy-suh-lawg, -log] / ˈaɪ səˌlɔg, -ˌlɒg /
Or isolog

noun

Chemistry.
  1. one of two or more isologous compounds.


Etymology

Origin of isologue

1885–90; back formation from isologous, on the model of homologue: homologous