Definition of tertium quid in US English:

tertium quid


  • A third thing that is indefinite and undefined but is related to two definite or known things.

    • ‘Unfortunately, given the interminability of the debate, only a few voices in the book seek to find a tertium quid - that is, a wider outlook that could lift the debate off its current hinges and onto a more illuminative level.’
    • ‘Unable to fully reconcile the cases, Justice Scalia said that the trade dress in Two Pesos was either some form of packaging, or tertium quid.’


Early 18th century: from late Latin, translation of Greek triton ti ‘some third thing’.


tertium quid