dual

• du. (abbreviation, grammar)

PIE word
*dwóh₁

Borrowed from Latin dualis (“two”), from duo (“two”) + adjective suffix -alis.

• (Received Pronunciation) enPR: dyo͞oʹəl, jo͞oʹəl
  • (yod-coalescence) IPA^(key): /ˈdʒuː.əl/
  • (without the yod-coalescence) IPA^(key): /ˈdjuː.əl/
• (General American) enPR: d(y)o͞o'əl; IPA^(key): /ˈdu.əl/, /ˈdju.əl/

• Audio (UK):

  (file)

• Rhymes: -uːəl
• Homophones: duel; jewel (yod-coalescence)

dual (not comparable)

1. Characterized by having two (usually equivalent) components.

   Synonyms: double, twin; see also Thesaurus:dual

   a dual-motor vehicle

2. Pertaining to two, pertaining to a pair of.

   Synonyms: double, duplicate; see also Thesaurus:twofold

   dual engine failure

   dual citizenship

   • 2020, Grace Ying May, “Women Disciplining Men: A Biblical Pattern of Leadership”, in Aída Besançon Spencer, William David Spencer, editors, Christian Egalitarian Leadership: Empowering the Whole Church According to the Scriptures, page 48:

     Both Deborah and Samuel held dual roles as judges and prophets.

   • 2021 March 15, Jessie Yeung, “These Asian countries are giving dual citizens an ultimatum on nationality – and loyalty”, in CNN‎^[1]:

     And some Asian countries are tightening their immigration laws. Japan reinforced its strict stance in January when a court upheld the country’s ban against dual citizenship, rejecting a lawsuit filed by Japanese citizens living in Europe.

3. (grammar) Pertaining to a grammatical number in certain languages that refers to two of something, such as a pair of shoes.

   Coordinate terms: singular, trial, plural

   Modern Arabic displays a dual number, as did Homeric Greek.

4. (mathematics, physics) Exhibiting duality.
5. (linear algebra) Being the space of all linear functionals of (some other space).
   • 2012, Doug Fisher, Hans-J. Lenz, Learning from Data: Artificial Intelligence and Statistics V, Springer Science & Business Media, →ISBN, page 81:

     Accordingly, a hyperplane in the sample space is dual to a subspace in the variable space.

6. (category theory) Being the dual of some other category; containing the same objects but with source and target reversed for all morphisms.

   Synonym: opposite

   • 1992, Colin McLarty, Elementary Categories, Elementary Toposes, Clarendon Press, →ISBN, page 77:

     Every category is dual to its own dual, so if a statement holds in all categories so does its dual.

dual (plural duals)

1. Of an item that is one of a pair, the other item in the pair.
2. (geometry) Of a regular polyhedron with V vertices and F faces, the regular polyhedron having F vertices and V faces.

   The octahedron is the dual of the cube.

3. (grammar) The dual number.
4. (mathematics) Of a vector in an inner product space, the linear functional corresponding to taking the inner product with that vector. The set of all duals is a vector space called the dual space.
5. (wrestling) A head-to-head match or meet between two teams, such as two high schools or colleges.
   • 2010 August 3, Kevin Revolinski, Insiders' Guide® to Madison, WI, Rowman & Littlefield, →ISBN, page 137:

     Wrestling duals and meets take place at the Wisconsin Field House. There are no advance single event ticket sales.

   • 2014 November 18, Mark Schultz, David Thomas, Foxcatcher: The True Story of My Brother's Murder, John du Pont's Madness, and the Quest for Olympic Gold, Penguin, →ISBN:

     But Dave agreed to participate in the Bulgarian dual, and that trapped me into having to wrestle, too.

   • 2023 October 19, Jason Norman, American Women in Amateur Wrestling, 2000-2022, McFarland, →ISBN, page 203:

     Early in 2021, she became the first female to compete and win a match at the Ter-Hark Cup wrestling dual, helping her squad to victory.

• (grammatical numbers) grammatical number; singular, dual, trial, quadral, quintal, paucal, plural ^{(Category: en:Grammar)}
• unal
• duel

dual (third-person singular simple present duals, present participle (UK) dualling or (US) dualing, simple past and past participle (UK) dualled or (US) dualed)

1. (transitive) To convert from single to dual; specifically, to convert a single-carriageway road to a dual carriageway.
   • 1994, Great Britain. Parliament. House of Commons, Parliamentary Debates:

     I have to declare an interest and I do so with some ambivalence because if the road is dualled it is likely to take half of my front garden.

   • 2006, David Lowe, Intermodal Freight Transport, page 163:

     The power generation and propulsion systems are dualled to accommodate component failure and maintain propulsion at reduced speed should any part of one system be lost.

   • 2021 September 22, “Network News: Nexus increases Tyne and Wear Metro train order to 46”, in RAIL, number 940, page 23:

     The investment will allow Nexus to increase service frequencies, reduce journey times, and improve reliability by dualling three sections of line between Pelaw and South Shields.

• Auld, Daul, Dula, auld, laud, udal

• Audio (France (Toulouse)):

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• Audio (France (Vosges)):

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• Audio (France (Lyon)):

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• Audio (France (Somain)):

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dual (feminine duale, masculine plural duaux, feminine plural duales)

1. dual

dual m (plural duaux)

1. dual

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

• IPA^(key): [duˈaːl]
• Hyphenation: du‧al

• Audio (Germany):

  (file)

• Rhymes: -aːl

dual (strong nominative masculine singular dualer, not comparable)

1. dual

• “dual” in Duden online
• “dual” in Digitales Wörterbuch der deutschen Sprache

• IPA^(key): /d̪ˠuəl̪ˠ/, /d̪ˠuəlˠ/

From Old Irish dúal (“tress, lock of hair”), from Proto-Celtic *doklos, from Proto-Indo-European *doḱlos (compare Icelandic tagl (“horse’s tail”), Old English tæġl, English tail).

dual m (genitive singular duail, nominative plural duail)

1. lock, tress

   Synonyms: dlaoi, dual gruaige

2. wisp, tuft

   Synonym: dlaoi

3. ply, strand
4. twist, twine
5. spiral, whirl

• dualach¹
• duailín, dualán

dual (present analytic dualann, future analytic dualfaidh, verbal noun dualadh, past participle dualta)

1. (transitive) twine
2. (transitive) braid, coil
3. (transitive) interlace, fold

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)

dual m (genitive singular duail, nominative plural duail)

1. dowel
2. knot (in timber)

   Synonyms: alt, cranra

• dualach²
• dualbhata

From Old Irish dúal (“that which belongs or is proper to an individual by nature or descent”), from Proto-Indo-European *dʰewgʰ-.

dual (genitive singular masculine duail, genitive singular feminine duaile, plural duala, comparative duaile)

1. native, natural

   Is dual dó a bheith leisciúil. ― He is naturally lazy.

   Ní dual don diabhal bheith díomhaoin.

   No rest for the wicked.

   (literally, “It is not in the devil's nature to be idle.”)

2. proper, fitting
3. in the natural order of things
4. fated
5. possible

• dualgas

• Ó Dónaill, Niall (1977), “dual”, in Foclóir Gaeilge–Béarla, Dublin: An Gúm, →ISBN
• Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 dúal”, in eDIL: Electronic Dictionary of the Irish Language
• Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “2 dúal”, in eDIL: Electronic Dictionary of the Irish Language
• de Bhaldraithe, Tomás (1959), “dual”, in English-Irish Dictionary, An Gúm
• Finck, F. N. (1899), Die araner mundart [The Aran Dialect] (in German), Zweiter Band: Wörterbuch [Second volume: Dictionary], Marburg: Elwert’sche Verlagsbuchhandlung, page 72
• “dual”, in New English-Irish Dictionary, Foras na Gaeilge, 2013–2025

• Rhymes: (Portugal) -al, (Brazil) -aw
• Hyphenation: du‧al

dual m or f (plural duais, not comparable)

1. dual (having two elements)

• dualidade
• dualmente

Borrowed from French duel, from Latin dualis.

dual n (plural duale)

1. (grammar) dual

From Old Irish dúal (“that which belongs or is proper to an individual by nature or descent”), from Proto-Indo-European *dʰewgʰ-.

• IPA^(key): /t̪uəɫ̪/

dual (comparative duaile)

1. hereditary
2. usual, natural

   'S dual do phoileasman a bhith amharasach. ― It's natural for a policeman to be suspicious.

• bu dual do dh'isean an ròin a dhol chun na mara

dual m (genitive singular duail, plural dualan)

1. birthright

   Synonym: còir-bhreith

2. due
3. something which is natural and/or usual

From Old Irish dúal (“tress, lock of hair”), from Proto-Celtic *doklos, from Proto-Indo-European *doḱlos.

dual m (genitive singular duail, plural dualan)

1. curl, lock of hair
2. plait, strand, braid, or fold
3. ringlet

dual (past dhual, future dualidh, verbal noun dualadh, past participle dualte)

1. plait, twist
2. loop, curl
3. fold
4. link

• MacBain, Alexander; Mackay, Eneas (1911), “dual”, in An Etymological Dictionary of the Gaelic Language‎^[2], Stirling, →ISBN, page 145

• Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 dúal”, in eDIL: Electronic Dictionary of the Irish Language
• Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “2 dúal”, in eDIL: Electronic Dictionary of the Irish Language

From Latin duālis.

• IPA^(key): /ˈdwal/ [ˈd̪wal]
• Rhymes: -al
• Syllabification: dual

dual m or f (masculine and feminine plural duales)

1. dual
2. (grammar) dual

• “dual”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8, Royal Spanish Academy [Spanish: Real Academia Española], 10 December 2024