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, 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?
Best Answer
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:
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.