allogeneous

At its base is Ancient Greek ἀλλογενής, allogenes, "of another race" or "of another kind". The adjective joins allos, "other", with genos, "birth, stock, kind". Greek used it for what did not belong to the native line or source.

Late antique and medieval learned writing preserved the Greek pattern in forms that moved through scholarly Latin. By the 17th and 18th centuries, European science favored such compounds when it needed exact labels for origin and difference. English inherited that habit and made adjectives like allogeneous for things produced from a different source.

The English form shows the ending -ous, which turns the inherited stem into a standard adjective. It sat beside near-relatives such as allogenous and allogeneic, each shaped by a slightly different scientific register. In geology, biology, and pathology, the word pointed to material or tissue that came from elsewhere.

Allogeneous never became common everyday English, but it remained useful where provenance mattered. Its force is not merely "different" but "different in source or generation". That old Greek sense of other birth still governs the modern word.