c

¹ American  

Or c.

abbreviation

1. (with a year) about.

   c1775.

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c ² American  

Or c.

abbreviation

1. Optics. candle; candles.

2. cycle; cycles.

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c ³ American  

Symbol.

1. Physics, Optics. the speed of light in a vacuum: standardized as 186,282.4 miles per second (299,792,458 meters per second).

2. Physics, Acoustics. the speed of sound.

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C ⁴ American  

[see] / si /

Or c

noun

plural

C's, Cs, c's, cs

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

2. any spoken sound represented by the letter C or c, as in cat, race, or circle.

3. something having the shape of a C .

4. a written or printed representation of the letter C or c.

5. a device, as a printer's type, for reproducing the letter C or c.

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C ⁵ American  

noun

1. Computers. a high-level programming language: very powerful and flexible, it is used in a wide variety of applications.

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C ⁶ American  

abbreviation

1. cocaine.

2. Grammar. complement.

3. consonant.

4. Electricity. coulomb.

5. county (used with a number to designate a county road).

   C55.

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C ⁷ American  

Symbol.

1. the third in order or in a series.

2. (in some grading systems) a grade or mark, as in school or college, indicating the quality of a student's work as fair or average. Sometimes c

3. Music.

   1. the first tone, or keynote, in the scale of C major or the third tone in the relative minor scale, A minor.

   2. a string, key, or pipe tuned to this tone.

   3. a written or printed note representing this tone.

   4. (in the fixed system of solmization) the first tone of the scale of C major, called do.

   5. the tonality having C as the tonic note.

   6. a symbol indicating quadruple time and appearing after the clef sign on a musical staff.

4. the Roman numeral for 100. Sometimes c

5. Celsius.

6. centigrade.

7. Electricity.

   1. capacitance.

   2. a battery size for 1.5 volt dry cells: diameter, 1 inch (2.5 centimeters); length, 1.9 inches (4.8 centimeters).

8. Chemistry. carbon.

9. Physics.

   1. charge conjugation

   2. charm.

10. Biochemistry.

    1. cysteine.

    2. cytosine.

11. Slang. Also a hundred-dollar bill.

12. a proportional shoe width size, narrower than D and wider than B.

13. a proportional brassiere cup size, smaller than D and larger than B.

14. the lowest quality rating for a corporate or municipal bond.

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c̄ ⁸ American  

Or c.

1. (in prescriptions) with.

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C- ⁹ American  

U.S. Military.

1. (in designations of transport aircraft) cargo.

   C-54; C-124.

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c. ¹⁰ American  

abbreviation

1. gallon.

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c. ¹¹ American  

abbreviation

1. Optics. candle; candles. Also c

2. carat.

3. carbon.

4. carton.

5. case.

6. Baseball. catcher.

7. cathode.

8. cent; cents.

9. centavo.

10. Football. center.

11. centigrade.

12. centime.

13. centimeter.

14. century.

15. chairman; chairperson.

16. chapter.

17. chief.

18. child.

19. church.

20. cirrus.

21. city.

22. cloudy.

23. cognate.

24. color.

25. copper.

26. copyright.

27. corps.

28. cubic.

29. cycle; cycles. Also c

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C. ¹² American  

abbreviation

1. Calorie.

2. Cape.

3. Catholic.

4. Celsius.

5. Celtic.

6. Centigrade.

7. College.

8. (in Costa Rica and El Salvador) colon; colons.

9. Congress.

10. Conservative.

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c/- ¹ British  

abbreviation

1. care of

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c. ² British  

abbreviation

1. carat

2. cricket caught

3. cent(s)

4. century or centuries

5. (used esp preceding a date) circa

   c. 1800

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C- ³ British  

abbreviation

1. cargo transport

   C-5

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C ⁴ British  

symbol

1. music

   1. a note having a frequency of 261.63 hertz ( middle C ) or this value multiplied or divided by any power of 2; the first degree of a major scale containing no sharps or flats ( C major )

   2. a key, string, or pipe producing this note

   3. the major or minor key having this note as its tonic

   4. a time signature denoting four crotchet beats to the bar See also alla breve common time

2. chem carbon

3. biochem cytosine

4. capacitance

5. heat capacity

6. cold (water)

7. physics compliance

8. Celsius

9. centigrade

10. century

    C20

11. coulomb

12. 100 See Roman numerals

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abbreviation

1. Cuba (international car registration)

noun

1. a computer programming language combining the advantages of a high-level language with the ability to address the computer at a level comparable with that of an assembly language

c ⁵ British  

symbol

1. centi-

2. cubic

3. cycle

4. maths constant

5. specific heat capacity

6. the speed of light and other types of electromagnetic radiation in a vacuum

7. chess See algebraic notation

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c ⁶ British  

/ siː /

noun

1. the third letter and second consonant of the modern English alphabet

2. a speech sound represented by this letter, in English usually either a voiceless alveolar fricative, as in cigar, or a voiceless velar stop, as in case

3. the third in a series, esp the third highest grade in an examination

4. 1. something shaped like a C

   2. ( in combination )

      a C-spring

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C. ⁷ British  

abbreviation

1. (on maps as part of name) Cape

2. Catholic

3. Celtic

4. Conservative

5. Corps

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c Scientific  

1. The symbol for the speed of light in a vacuum.

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Etymology

Origin of c¹

From Latin circā, circiter, circum

Origin of c̄⁸

From the Latin word cum

Origin of c.¹⁰

From the Latin word congius

Example Sentences

Here, E again represents energy, m is the particle's mass, and c is the speed of light.

From Science Daily • Mar. 10, 2026

Not every editor is quite as catholic with a little c, as ecumenical, as excited about such a range of writing as I am.

From Los Angeles Times • Feb. 13, 2026

Clear signs of sulfur were found on the third planet, HR 8799 c, and the researchers believe it likely exists on the other two inner planets as well.

From Science Daily • Feb. 11, 2026

This is often what I'd describe as campaigning with a small "c" – discreet conversations and planning, the vast majority a long way from the public gaze and deniable.

From BBC • Dec. 30, 2025

Namely, because Pacheco could not stand the way Onofre, reading aloud in Spanish, pronounced his c s and z’s.

From "The Milagro Beanfield War" by John Nichols

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