duale tantum

plural dualia tantum

1. grammarA noun (or specific sense of a noun) that can only occur in the dual, and which lacks forms for singular, plural, and any other number.

   The second -c- refers to icgaʹkwal “eel” (duale tantum), a form used alongside of igaʹkwal (masc.).

   1909, Edward Sapir, Wishram Texts, page 4, footnote 1

   2 more examples

   The only natural-pair noun consistently preferring the dual over the plural, ὄσσε, virtually a duale tantum, refers to the eyes not as mere sense-organs but as ‘windows of the soul’.

   1989, Frans Plank, “On Humboldt on the Dual” in Linguistic Categorization, eds. R. Corrigan, F.R. Eckman, and M.P. Noonan, § 2.5, 309

   Generally singularia tantum are the most common; we find instances with just the plural or with dual and plural but lacking the singular; dualia tantum are quite rare.

   2000, Greville G. Corbett, Number, chapter v, § 5.8.2, 175