c

UK: 'C', 'c': /ˈsiː/ US: 'C', 'c': /si/ ,'C', 'c': (sē)

Collins Concise English Dictionary © HarperCollins Publishers::

c, C / siː/ noun (c's, C's, Cs)

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. something shaped like a C

c symbol

1. centi-
2. cubic
3. cycle
4. constant
5. specific heat capacity
6. the speed of light and other types of electromagnetic radiation in a vacuum

WordReference Random House Learner's Dictionary of American English © 2025

C, c /si/   n. [countable] , pl. Cs or C's, cs or c's. 

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

C,  Symbol.

1. Education [sometimes: c] (in some grading systems) a grade or mark indicating fair or average quality.
2. Music and Dance
   • the tonic note of the C major scale.
   • a written or printed note representing this tone.
3. [sometimes: c] the Roman numeral for 100.
4. Physics Celsius:
   The temperature is 10°C (said as "10 degrees Celsius'').
5. Physics centigrade.
6. Chemistry carbon.
7. Also, C-note. Slang. a hundred-dollar bill.

c,  an abbreviation of: circa

1. (used with a year):
   c1775.

c, [Symbol.]

1. Optics, Physics the velocity of light in a vacuum: approximately 186,000 miles per second or 299,793 kilometers per second.
2. Physics the velocity of sound.

C.,  an abbreviation of:

1. Thermodynamics Calorie.
2. Education College.
3. Conservative.

c.,  an abbreviation of:

1. Thermodynamics calorie.
2. Jewelry carat.
3. Physics centigrade.
4. Weights and Measures centimeter.
5. chapter.
6. circa (used with a year):
   c. 1775.
7. copyright.
8. Weights and Measures cubic.

WordReference Random House Learner's Dictionary of American English © 2025

ˈRo•man ˈnu•mer•al,  n. [countable]

1. any of the numerals in the ancient Roman system of notation, still used occasionally. The basic symbols are I (=1), V (=5), X (=10), L (=50), C (=100), D (=500), and M (=1000).

WordReference Random House Unabridged Dictionary of American English © 2025

C, c  (sē), n., pl. C's or Cs, c's or 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 aC.
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.

C, 

1. Drugs cocaine.
2. Education, Grammar [Gram.] complement.
3. Music and Dance consonant.
4. Physics coulomb.
5. county (used with a number to designate a county road):
   C55.

C,  Symbol.

1. the third in order or in a series.
2. (sometimes l.c.) (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.
3. [Music.]
   • Phonetics the first tone, or keynote, in the scale of C major or the third tone in the relative minor scale, A minor.
   • Music and Dance a string, key, or pipe tuned to this tone.
   • Phonetics a written or printed note representing this tone.
   • (in the fixed system of solmization) the first tone of the scale of C major, called do.
   • the tonality having C as the tonic note.
   • a symbol indicating quadruple time and appearing after the clef sign on a musical staff.
4. (sometimes l.c.) the Roman numeral for 100.
5. Celsius.
6. centigrade.
7. [Elect.]
   • capacitance.
   • a battery size for 1.5 volt dry cells: diameter, 1 in. (2.5 cm);
     length, 1.9 in. (4.8 cm).
8. Chemistry carbon.
9. [Physics.]
   • charge conjugation.
   • charm¹ (def. 9).
10. [Biochem.]
    • cysteine.
    • cytosine.
11. Also, C-note. [Slang.] a hundred-dollar bill.
12. Clothing a proportional shoe width size, narrower than D and wider than B.
13. Clothing a proportional brassiere cup size, smaller than D and larger than B.
14. Stock Exchange, Business the lowest quality rating for a corporate or municipal bond.
15. Computing a high-level programming language: very powerful and flexible, it is used in a wide variety of applications.

c, 

1. Drugs calorie.
2. [Optics.] candle;
   candles.
3. (with a year) about:
   c1775.
• Latin circā, circiter, circum
4. [Physics, Chem.] curie;
   curies.
5. cycle;
   cycles.

c,  Symbol.

1. [Optics, Physics.] the velocity of light in a vacuum: approximately 186,000 miles per second or 299,793 kilometers per second.
2. Physics [Acoustics, Physics.] the velocity of sound.

c̄, 

1. (in prescriptions) with.

• Latin cum

C., 

1. Calorie.
2. Place Names Cape.
3. Religion Catholic.
4. Physics Celsius.
5. Celtic.
6. Physics Centigrade.
7. Education College.
8. Currency (in Costa Rica and El Salvador) colon;
   colons.
9. Government Congress.
10. Government Conservative.

C-, [U.S. Mil.]

1. Military (in designations of transport aircraft) cargo:
   C-54; C-124.

c., 

1. calorie.
2. Optics candle;
   candles.
3. Jewelry carat.
4. Chemistry carbon.
5. carton.
6. case.
7. [Baseball.] catcher.
8. Electricity cathode.
9. Currency cent;
   cents.
10. Currency centavo.
11. [Football.] center.
12. Physics centigrade.
13. Currency centime.
14. Weights and Measures centimeter.
15. century.
16. chairman;
    chairperson.
17. chapter.
18. chief.
19. child.
20. church.
21. (with a year) about:
    c. 1775.
• Latin circā, circiter, circum
22. Meteorology cirrus.
23. city.
24. cloudy.
25. Linguistics cognate.
26. color.
27. Weights and Measures gallon.
• Latin circā, circiter, circum
28. Chemistry copper.
29. copyright.
30. corps.
31. Weights and Measures cubic.
32. (in prescriptions) with.
• Latin circā, circiter, circum
33. cycle;
    cycles.

C++, n. 

1. Computing a high-level programming language, a descendant of C, with the ability to manipulate object-oriented features.

WordReference Random House Unabridged Dictionary of American English © 2025

Ro′man nu′merals, 

1. the numerals in the ancient Roman system of notation, still used for certain limited purposes, as in some pagination, dates on buildings, etc. The common basic symbols are I (=1), V (=5), X (=10), L (=50), C (=100), D (=500), and M (=1000). The Roman numerals for one to nine are: I, II, III, IV, V, VI, VII, VIII, IX. A bar over a letter multiplies it by 1000;
   thus, X̄ equals 10,000. Integers are written according to these two rules: If a letter is immediately followed by one of equal or lesser value, the two values are added;
   thus, XX equals 20, XV equals 15, VI equals 6. If a letter is immediately followed by one of greater value, the first is subtracted from the second;
   thus, IV equals 4, XL equals 40, CM equals 900. Examples: XLVII(=47), CXVI(=116), MCXX(=1120), MCMXIV(=1914). Roman numerals may be written in lowercase letters, though they appear more commonly in capitals.

• 1725–35

Collins Concise English Dictionary © HarperCollins Publishers::

C symbol

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. the major or minor key having this note as its tonic
3. a time signature denoting four crotchet beats to the bar
   See also alla breve2, common time
4. carbon
5. cytosine
6. capacitance
7. heat capacity
8. cold (water)
9. compliance
10. Celsius
11. centigrade
12. century: C21
13. coulomb
14. (Roman numeral) 100
    See Roman numerals

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

Collins Concise English Dictionary © HarperCollins Publishers::

C. abbreviation

1. (on maps as part of name) Cape
2. Catholic
3. Celtic
4. Conservative
5. Corps

Collins Concise English Dictionary © HarperCollins Publishers::

c. abbreviation

1. carat
2. caught
3. cent(s)
4. century or centuries
5. (used esp preceding a date) circa: c. 1800

Etymology: (for sense 5) Latin: about