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. (on maps as part of name) Cape

2. Catholic

3. Celtic

4. Conservative

5. Corps

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c ² 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- ³ British  

abbreviation

1. cargo transport

   C-5

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c ⁴ 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/- ⁵ British  

abbreviation

1. care of

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C ⁶ 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. ⁷ 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 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

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

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

While the Englishman spoke up for conservatives with a small c, the American emerged into a new style of politics: His literary success was inseparable from his activism as a promoter of gay rights.

From The Wall Street Journal • Dec. 12, 2025

"While we can't yet confirm the presence of an atmosphere or life on GJ 251 c, the planet represents a promising target for future exploration," Mahadevan said.

From Science Daily • Nov. 13, 2025

One minor modification that readers will already have noticed is that the Semitic and Greek g became the Roman and English c, while the Romans invented a new g in its present position.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

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