Definition of Theria in US English:

Theria

plural noun

Zoology
  • A major group of mammals that comprises the marsupials and placentals.

    Subclass Theria, class Mammalia

    Compare with Prototheria
    • ‘It is therefore puzzling that such adaptations appear to have a limited distribution within the Theria.’

Origin

Modern Latin (plural), from Greek thēria ‘wild animals’.

Pronunciation

Theria

/ˈTHirēə/