Isologous \I*sol"o*gous\, a. [Iso- + Gr. lo`gos 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.
[1913 Webster]