vergence

From verge (“tend, incline”, from Latin vergere) +‎ -ence, synonym of earlier (1660s) vergency (the equivalent of French vergence). Coined as a technical term in ophthalmology, as a hyperonym of convergence and divergence, in 1902. The sense of the numeric quantity in geometric optics was introduced, from use of the term in physiological optics, in the 1920s.

vergence (countable and uncountable, plural vergences)

1. (physiology) The simultaneous turning of both eyes when focusing. [1902]
2. (optics) A measure of convergence or divergence of rays. [c. 1920]
   • 1921, The Optician and Scientific Instrument Maker, volume 62, page 1:
     • "a special vertex trial case computed for an object vergence of 4.00."
   • 1947 Benjamin King Johnson, Optics and Optical Instruments: An Introduction with Special Reference to Practical Applications, Courier Corporation (1960 [1947]), p. 152.
     • "Ample movement between the source and condenser should be available in order to allow for a variation in the vergence of the light leaving the condenser"
3. (geology) The direction of the overturned component of an asymmetric fold.

1738, glosses New Latin vergentia in the Latin translations of Hippocrates (16th century).

• IPA^(key): /vɛʁ.ʒɑ̃s/

vergence f (plural vergences)

1. (dated, medicine) the quality of being inclined or tending towards something [1738]
   • 1738 Philippe Hecquet, La medecine naturelle chez Guillaume Cavelier, p. 646.
     • "il [Hippocrate] recommande de bien s'assurer de la vergence des humeurs, cest-a-dire, d'où elles partent & vers où elles tendent."
   • 1740 Philippe Hecquet, La medecine, la chirurgie, et la pharmacie des pauvres, t. 2, chez la Veuve Alix, p. 354.
     • "C'est que, suivant le langage d'Hippocrate, l'on ne sçauroit avoir trop d'égard à la vergence des humeurs en fait de purgation, quò vergunt humores eò ducendi."
2. (physiology) vergence, the simultaneous turning of both eyes when focusing.
3. (optics) vergence, a measure of convergence or divergence of rays. [c. 1920]
   • 1924, M. Dufour, “Le rôle de la vergence en dioptrique”, in Annales d'oculistique, Paris:

• “vergence”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.