dual

American  

[doo-uhl, dyoo-] / ˈdu əl, ˈdju- /

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

• 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

Grace is a senior at Harvard University, where she pursues a dual concentration in Economics and English.

From The Wall Street Journal • Jul. 6, 2026

The Fed has a dual mandate of keeping inflation to a long-term two-percent target while also ensuring maximum employment.

From Barron's • Jul. 1, 2026

Information on its website tells prospective customers they would sit in the front of the aircraft with access to "dual flight controls under the guidance of your fully certified and highly skilled flight instructor".

From BBC • Jul. 1, 2026

Meanwhile, the bathroom boasts a glass-enclosed shower and a dual vanity.

From MarketWatch • Jun. 29, 2026

Points and lines are dual to each other.

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