I remember being taught in history classes to abbreviate century by writing a large capital C followed by the ordinal number as in: C18th without the full-stop (period).

Recently I have noticed on ELU (it wasn't something I paid particular attention in the past) the lower-case c after a cardinal number and with a period, as in: 18c. and 18c without the period. Would either 18th c. or C18 be considered incorrect?

I checked online and The Oxford English Dictionary says century is abbreviated thus: c. but no indication if the number preceding should be ordinal or cardinal. On the first page of Google results I also found the Monash University recommended symbol, enter image description here but without th.

In The Chambers Dictionary 12th Edition, it lists both C and c as abbreviations for century:

C (preceding numeral, eg C21, twenty-first century)

c (following numeral, eg 21c, twenty-first century)

It also lists:

cen. abbrev: central; century

cent. abbrev: centigrade; central; centum (L), a hundred; century.

Why is the ordinal number e.g. 18th, 21st ignored? And finally, which is the most commonly accepted and recommended abbreviation?

  • I have never seen 18th c., neither has nGram. 18c. would be understandable :)
    – mplungjan
    Dec 5, 2013 at 9:03
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    Ngram doesn't prove that people don't write 18th c. It is after all an abbreviation, and if I were writing a book or an essay I would never abbreviate 'century'.
    – Mari-Lou A
    Dec 5, 2013 at 9:05
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    C18 may refer to: . . . The 18th century (1701-1800AD) [Wikipedia]. // And from AHDEL: century n. . . . Abbr. C. or c. or cent. _ which I think licenses 18th C. etc. Also, I've found a source advocating dropping periods from abbreviations. Choose one you like and try to be consistent. Dec 5, 2013 at 9:16
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    I will join mplungjan with my personal experience: I too see 18c. (with or without spaces and dot) very commonly, but I do not recall ever seeing C18 before. I would assume that to be a section in a library or something along those lines. Dec 5, 2013 at 11:48
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    @Mari-LouA Interesting that the OP in that question left her own question because someone dared mention BC/AD <shakes head>
    – mplungjan
    Dec 5, 2013 at 12:35

4 Answers 4


You're asking a question about style, as such you're more likely to find a satisfactory answer outside of the dictionary.

The Associated Press Style Manual doesn't address century specifically, but says you should "Never use an abbreviation that will not be easily understood."

Wikipedia's Manual of Style has a variety of related statements:

  • "Centuries and millennia not in quotes or titles should be either spelled out (eighth century) or in Arabic numeral(s) (8th century). The same style should be used throughout any article."
  • "To indicate around, approximately, or about, the unitalicised abbreviation c. is preferred over circa, ca, ca., approximately, or approx., and should be spaced (c. 1291). Do not use a question mark for this function (1291?), as this may imply to the reader an uncertainty on the part of Wikipedia editors rather than on the part of reliable historians."
  • "Standard symbols for units are undotted; e.g. m for the metre (not m.), kg for the kilogram (not kg.), in for the inch (not in., the quotation mark ", or the double prime ″), and ft for foot (not ft., the apostrophe ', or the prime ′).
    • Non-standard abbreviations should be dotted."

The Association of American Colleges and Universities Style Guide discusses this issue directly: "Centuries are spelled out (CMS 9.33): the twenty-first century"

I'm sure you can find others, but to my way of thinking, your best bet is to either not abbreviate century, or use something unambiguous (such as "cent.") if you have to use an abbreviation.


The Chicago Manual of Style (16th ed., section 10.43) uses c. to abbreviate century, and advises that it is used only "in bibliographic references, glossaries, and other scholarly apparatus." I use in in scholarly book/journal indexes. For example, one sub-entry is "interpretations of (15c.–18c.)"

  • What is CMS, please? Chicago manual style? (I've only just woken up from my nap) If it is, could you please write its full name and I'll upvote your answer. (btw what's 10.43?)
    – Mari-Lou A
    Nov 12, 2014 at 16:19
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    @Mari-LouA OP should definitely edit to include a better description of his reference, but CMS (usually CMOS) is indeed the Chicago Manual of Style, and 10.43 refers to chapter 10, subsection/point 43, which is obvious to anyone familiar with Chicago but otherwise rather opaque. Nov 12, 2014 at 16:41
  • Better late than never...
    – Mari-Lou A
    Apr 19, 2017 at 21:17

FWIW, when I was taught (by History teachers) to take lecture notes as a VIth Form A-level student in Britain in the 1970s, we were taught the abbreviation "C12th" etc. as a standard usage (optionally with the C larger than and partially enclosing the number). Several teachers with different academic backgrounds used this form of abbreviation on blackboards, handouts etc. However, we weren't allowed to use it in essays/formal writing. It's a note-taking or informal usage shorthand. I never saw the "15C/c" form until recently on the Internet and I think that is unclear and potentially confusing whereas the capital C plus number with abbreviated ordinal indicator is pretty unequivocal and obvious. I've used the "C20th" form often in varied contexts ever since and can't recall ever being asked to explain it, so it clearly it has good recognition/obvious meaning.


I was taught XXI or 21c. for twenty first century. The most important part being that the reader understands the writers intention.

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