Jump To:

• j
  j

  a unit vector on the y-axis of a coordinate system.
• J
  J

  noun

  the tenth letter of the English alphabet, a consonant.
• J.
  J.

  abbreviation

  Jack.

j

¹ American  

Symbol.

1. Mathematics. a unit vector on the y-axis of a coordinate system.

2. Engineering. the imaginary number .

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J ² American  

[jey] / dʒeɪ /

Or j

noun

J's, plural Js, plural j's, plural js plural

1. the tenth letter of the English alphabet, a consonant.

2. any spoken sound represented by the letter J or j, as in just, major, or rajah.

3. something having the shape of a J .

4. a written or printed representation of the letter J or j.

5. a device, as a printer's type, for reproducing the letter J or j.

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J ³ American  

abbreviation

1. Jewish.

2. Physics. joule; joules. Also j

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J ⁴ American  

Symbol.

1. the tenth in order or in a series.

2. (sometimes lowercase) the medieval Roman numeral for 1.

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J. ⁵ American  

abbreviation

1. Cards. Jack.

2. Journal.

3. Judge.

4. Justice.

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j ¹ British  

/ dʒeɪ /

noun

1. the tenth letter and seventh consonant of the modern English alphabet

2. a speech sound represented by this letter, in English usually a voiced palato-alveolar affricate, as in jam

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J ² British  

symbol

1. cards jack

2. joule(s)

3. current density

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abbreviation

1. Japan (international car registration)

j ³ British  

symbol

1. maths the unit vector along the y -axis

2. Also called: i.  obsolete the imaginary number √–1

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J Scientific  

1. Abbreviation of joule

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Other Word Forms

Inflected Forms

noun

• j's
  plural
• J's
  plural
• Js
  plural
• js
  plural

Example Sentences

The two older boys, J and N, received three-year YROs with 180 days of intensive supervision.

From BBC • Jun. 5, 2026

Last month it introduced Reign, an umbrella brand for women’s sports projects such as a forthcoming podcast hosted by TikTok creator Coach Jackie J and “Courtside,” a women’s basketball rom-com in development.

From The Wall Street Journal • Jun. 4, 2026

She told Dias that they just didn’t have the money to stand up to Henry J Kaiser.

From Los Angeles Times • Mar. 26, 2026

Radio programmes such as Triple J and ABC Classic are expected to have limited live elements and play music only.

From BBC • Mar. 24, 2026

Dad tells Aunt J and Arlo what happened in the car.

From "Split the Sky" by Marie Arnold