Webster’s Revised Unabridged Dictionary · 1913
Isologous
I·sol′o·gous (ī·sŏl′ō·gŭs), a. [Iso- + Gr. λόγος proportion.] (Chem.) Having similar proportions, similar relations, or similar differences of composition; — said specifically of groups or series which differ by a constant difference; as, ethane, ethylene, and acetylene, or their analogous compounds, form an isologous series.