• WordNet 3.6
    • n duad two items of the same kind
    • ***
Webster's Revised Unabridged Dictionary
    • n Duad A union of two; duality.
    • ***
Century Dictionary and Cyclopedia
    • n duad Same as dyad.
    • n duad In mathematics, an unordered, pair; two objects considered as making up one, and as the same one whichever is taken first.
    • ***
Chambers's Twentieth Century Dictionary
    • ns Duad a pair of objects looked at as one
    • ***


Webster's Revised Unabridged Dictionary
See Dyad
Chambers's Twentieth Century Dictionary
L.,—duo, two.


In literature:

From the monad proceeds an indefinite duad, which is subordinate to the monad as to its cause.
"A History of Science, Volume 1(of 5)" by Henry Smith Williams
The Duad, with the Monad brooding behind it, is the fundamental principle of the Avesta.
"Ten Great Religions" by James Freeman Clarke
On the hyper level the triplet becomes a duad and a unit; the duad becomes two units; and the septet a triplet and a quartet.
"Occult Chemistry" by Annie Besant and Charles W. Leadbeater
The duad represented the line, as being bounded by two points or monads.
"Notes and Queries, Number 77, April 19, 1851" by Various

In science:

Each fragment contains both AAs and CLs. (D) Count the occurrence number of CL duad.
Hydropathy Conformational Letter and its Substitution Matrix HP-CLESUM: an Application to Protein Structural Alignment