quaternity

noun4

1. •
   A group or set of four; a foursome, a quartet.
2. •
   (historical) A group of four persons forming the Godhead, in contrast to the Trinity comprising three persons.

   • [H]e is bounden to beleue in yͤ trinitie. And yͤ felowe beleueth in a quaternitie. That is ꝙ [quod, i.e., quoth] I yͤ hole trinite ⁊ one moe. — 1528
3. •
   Synonym of fourness (“the property or state of being four in number”).

   • Some that in mystical quaternity / All Deity existed; and the first / Y'cleped Ineffable, and the last, Truth; / Father and Son, gods intermediate. — 1848
4. •
   (no longer used, rare) Synonym of quarter (“a fourth part”).

   • The first vvith divers crooks and turnings vvries, / Cutting the tovvn in foure quaternities; / But both joyn to resist invading enemies. — 1633