quaternity

noun

1. (countable, uncountable)A group or set of four; a foursome, a quartet.

   “[T]heir VVhole Scale, of all that is above the Body, vvas indeed not a Trinity, but a Quaternity, or Four Ranks and Degrees of Beings, one belovv another; the Firſt of Henades or Unities, the Second of Noes, Minds or Intellects, the Third of Souls, and the Laſt of Natures: theſe being as it vvere ſo many Orbs and Spheres, one vvithin and belovv another.”

2. (countable, historical, uncountable)A group or set of four; a foursome, a quartet.

   “[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.”

3. (countable, obsolete, rare, uncountable)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.”

4. (uncountable)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.”