Etymology PIE word *dwóh₁ Borrowed from Latin dualis (“two”), from duo (“two”) + adjective suffix -alis.
1
Characterized by having two (usually equivalent) components.
a dual-motor vehicle
2
Pertaining to two, pertaining to a pair of.
dual engine failure
dual citizenship
2 more examples
Both Deborah and Samuel held dual roles as judges and prophets.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:
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.2021 March 15, Jessie Yeung, “These Asian countries are giving dual citizens an ultimatum on nationality – and loyalty”, in CNN:
3
Grammar, Human sciences, Linguistics, Sciences Pertaining to a grammatical number in certain languages that refers to two of something, such as a pair of shoes.
Modern Arabic displays a dual number, as did Homeric Greek.
Linear algebra, Mathematics, Sciences Being the space of all linear functionals of (some other space).
Accordingly, a hyperplane in the sample space is dual to a subspace in the variable space.2012, Doug Fisher, Hans-J. Lenz, Learning from Data: Artificial Intelligence and Statistics V, Springer Science & Business Media, →ISBN, page 81:
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Category theory, Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences Being the dual of some other category; containing the same objects but with source and target reversed for all morphisms.
Every category is dual to its own dual, so if a statement holds in all categories so does its dual.1992, Colin McLarty, Elementary Categories, Elementary Toposes, Clarendon Press, →ISBN, page 77:
Mathematics, Sciences 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.
Wrestling duals and meets take place at the Wisconsin Field House. There are no advance single event ticket sales.2010 August 3, Kevin Revolinski, Insiders' Guide® to Madison, WI, Rowman & Littlefield, →ISBN, page 137:
But Dave agreed to participate in the Bulgarian dual, and that trapped me into having to wrestle, too.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:
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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.2023 October 19, Jason Norman, American Women in Amateur Wrestling, 2000-2022, McFarland, →ISBN, page 203:
Etymology PIE word *dwóh₁ Borrowed from Latin dualis (“two”), from duo (“two”) + adjective suffix -alis.
1
To convert from single to dual; specifically, to convert a single-carriageway road to a dual carriageway.
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.1994, Great Britain. Parliament. House of Commons, Parliamentary Debates:
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.2006, David Lowe, Intermodal Freight Transport, page 163:
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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.2021 September 22, “Network News: Nexus increases Tyne and Wear Metro train order to 46”, in RAIL, number 940, page 23: