biplicity

From Latin bi- (“twice”). Bailey (1736) suggests borrowing from Latin biplicitas, but this is not well attested. Compare duplicity, from Latin duplicare (“double”).

biplicity (uncountable)

1. The state of being twice folded; reduplication.
   • 1964, Robert Day Allen, Noburō Kamiya, Primitive Motile Systems in Cell Biology, page 610:

     […] that certain characteristic properties of the bacterial flagellum can be imitated in a wire coil model. These properties are: (1) the arc which is visible frequently at the end of a flagellum (Figs. 10 and 11), and (2) the phenomenon of “biplicity,” that is, the sudden appearance of one-half the usual pitch (Fig. 12).

2. Doubleness, the state of being double.
   • 1878, Edmund Montgomery, “Monera, and the problem of life”, in The Popular Science Monthly‎, volume XIII, page 680:

     The integration and differentiation of vital function on the one hand, and the preparation and composition of food-material on the other hand form — as we will become fully aware further on — the two great divisions in the subject-matter of the science of organization, divisions corresponding to the fundamental biplicity of all advanced organization, its animal and its vegetative life.

   • 1894, James Hutchison Stirling, Darwinianism: Workmen and Work‎, pages 111-12:

     He who reads them will see that Mr. Darwin by no means minces matters with Lyell […] There may be a certain biplicity of kindness and courtesy in Mr. Darwin ; but there is no duplicity of his essential manhood and truth.

• “biplicity”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• Nathan Bailey (1736) Dictionarium Britanicum: Or a More Compleat Universal Etymological English Dictionary Than Any Extant.