dual

American  

[doo-uhl, dyoo-] / ˈdu əl, ˈdyu- /

adjective

1. of, relating to, or noting two.

2. composed or consisting of two people, items, parts, etc., together; twofold; double.

   dual ownership;

   dual controls on a plane.

3. having a twofold, or double, character or nature.

4. Grammar. being or pertaining to a member of the category of number, as in Old English, Old Russian, or Arabic, that denotes two of the things in question.

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noun

Grammar.

1. the dual number.

2. a form in the dual, as Old English git “you two,” as contrasted with ge “you” referring to three or more.

dual British  

/ ˈdjuːəl /

adjective

1. relating to or denoting two

2. twofold; double

3. (in the grammar of Old English, Ancient Greek, and certain other languages) denoting a form of a word indicating that exactly two referents are being referred to

4. maths logic (of structures or expressions) having the property that the interchange of certain pairs of terms, and usually the distribution of negation, yields equivalent structures or expressions

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noun

1. grammar

   1. the dual number

   2. a dual form of a word

verb

1. (tr) to make (a road) into a dual carriageway

Other Word Forms

Derived Forms

• dually
  adverb

Etymology

Origin of dual

First recorded in 1535–45; from Latin duālis “containing two, relating to a pair,” equivalent to du(o) two + -ālis -al ¹

Explanation

Dual means double, or having two elements. If you have a dual major, it means you're majoring in two subjects, like astronomy and microbiology. The adjective dual comes from the Latin duo, for two, and means having two parts. You can have a dual purpose, following two goals at once. To copilot an airplane, you need a cockpit with dual controls. If you're sometimes nasty and sometimes sugar sweet, people might think you have a dual personality. Don't confuse dual, though, with duel, which is a fight between two people.

Example Sentences

I’m moving to Canada or Iceland or the south of France; I need to find my grandmother’s birth certificate and apply for dual citizenship.

From Salon • May 31, 2026

Yet I struggle with the notion that the SS has a dual identity as daily driver and weekend toy.

From The Wall Street Journal • May 30, 2026

That’s when her mother, Jeannette, 45, first heard about college dual enrollment.

From Los Angeles Times • May 28, 2026

On this basis, typical annual bills for dual fuel direct debit households under the current energy cap would be £1,490.

From BBC • May 27, 2026

Points and lines are dual to each other.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife