k

¹ American  

Symbol.

1. Mathematics. a vector on the z-axis, having length 1 unit.

2. Boltzmann constant.

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K ² American  

abbreviation

Ecology.

1. carrying capacity.

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K ³ American  

[key] / keɪ /

Or k

noun

plural

K's, Ks, k's, ks

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

2. any sound represented by the letter K or k, as in bilk, kit, or sick.

3. something having the shape of a K .

4. a written or printed representation of the letter K or k.

5. a device, as a printer's type, for reproducing the letter K or k.

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K ⁴ American  

abbreviation

1. the number 1000.

   The salary offered is $20K.

2. kilometer, especially in a footrace or wheelchair race on a road or track.

   She’s training to run her first 10K this summer.

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K ⁵ American  

abbreviation

1. Chess. king.

2. Physics. Kelvin.

3. Music. Köchel listing.

4. kindergarten.

   a K–12 boarding school.

5. Real Estate. kitchen.

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K ⁶ American  

Symbol.

1. the eleventh in order or in a series.

2. Computers.

   1. the number 1024 or 2 10 .

      A binary 32K memory has 32,768 positions.

   2. kilobyte.

3. Baseball. strikeout; strikeouts.

4. Physics. kaon.

5. Biochemistry. lysine.

6. Chemistry. potassium.

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k. ⁷ American  

abbreviation

1. Electricity. capacity.

2. karat.

3. kilogram; kilograms.

4. Chess. king.

5. knight.

6. knot.

7. kopeck.

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K. ⁸ American  

abbreviation

1. kip; kips.

2. Knight.

3. kwacha.

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K ¹ British  

symbol

1. kelvin(s)

2. chess king

3. chem potassium

4. physics kaon

5. currency

   1. kina

   2. kip

   3. kopeck

   4. kwacha

   5. kyat

6. one thousand

7. computing

   1. a unit of 1024 words, bits, or bytes

   2. (not in technical usage) 1000

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abbreviation

1. Cambodia (international car registration)

k ² British  

/ keɪ /

noun

1. the 11th letter and 8th consonant of the modern English alphabet

2. a speech sound represented by this letter, usually a voiceless velar stop, as in kitten

3. See five Ks

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k ³ British  

symbol

1. kilo(s)

2. maths the unit vector along the z-axis

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K ⁴ British  

abbreviation

1. Köchel: indicating the serial number in the catalogue (1862) of the works of Mozart made by Ludwig von Köchel (1800–77)

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Etymology

Origin of K⁴

Abbreviation of kilo- K ² for def. 1; abbreviation of kilometer ( def. ) K ² for def. 2

Origin of K⁶

K ⁴ def. 6 from German Kalium

Example Sentences

The economy has shifted from a lowercase k to an uppercase one, a Wall Street researcher told me this past week.

From Barron's • Dec. 4, 2025

The track she was looking at, later labelled k, was evidence of an unknown particle, now known as the kaon or K meson.

From BBC • Jul. 23, 2024

Repeat this algorithm for all one-digit numerical values of i, j and k, and the result will always be either a happy or a sad number.

From Scientific American • Oct. 24, 2023

He then shared a story how when he was younger, he once got the letters x,y, z and k in Scrabble — and spent 15 minutes determined to try to make a move.

From Washington Times • Oct. 26, 2022

But have you ever wondered why there's a k in garlicky when there isn’t one in garlic?

From "Woe Is I" by Patricia T. O'Conner