Heterogeneous means consisting of dissimilar elements. It’s the opposite of homogeneous (which is different from homogenous). Heterogenous, without the third e, is a biology term meaning (1) not originating within the body, and (2) of foreign origin. Most of us will never have to use heterogenous, which is so rare that some dictionaries don’t list it. Others list it as a variant of heterogeneous. Whatever the dictionaries say, careful writers keep the words separate.
The noun corresponding to heterogeneous is heterogeneity. Heterogenous‘s noun is heterogeny.
Examples
Here are a couple of rare examples of heterogenous used well:
Post-transplant lymphoproliferative disease (PTLD) is a morphologically heterogeneous group of lymphoid proliferations of varying clonal composition seen following bone marrow or solid organ transplantation. [Nature]
Signal characteristics in MRI and the heterogenous tumor blushin angiography suggested other possibilities. [European Journal of Cardio-Thoracic Surgery]
This isn’t comfortable territory for nonscientists, so most of us will never have to use heterogenous.
And these writers use the far more common heterogeneous well:
To succeed in a global marketplace, future managers need to fine-tune their ability to collaborate with and lead heterogeneous teams. [Fortune]
… they’re minimalist, like his Imagism, a heterogeneous mixture of the colloquial and arcane, foreign languages and others’ voices, like the “Cantos.” [Wall Street Journal]
Members of this heterogeneous population may wed from each other, but they never or seldom agree on anything. [American Chronicle]
