I am under the impression that both coterminous and conterminous have exactly the same meaning. There was a remark that Latin purists prefer conterminous. Why?

Is there any significant difference between the two? Do co- and con- have same effect on words?

I am looking for any additional information about these two words which would help me understand them better.


Yes, conterminous and coterminous both mean "to share a boundary".

According to the entries for co- and con-, below, co- is an Anglicising of con-, which is possibly why Latin purists prefer con-

In this instance co- and con- both mean together or with.

Etymology of co-

in Latin, the form of com- in compounds with stems beginning in vowels and h- and gn- (see com-). Taken in English from 17c. as a living prefix meaning “together, mutually, in common,” and used promiscuously with native words and Latin-derived words not beginning with vowels, sometimes even with words already having it (e.g. co-conspiritor).

Etymology of con-

prefix meaning "together, with," sometimes merely intensive; the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations, co- tends to be used where Latin would use con- (e.g. costar).

  • 1
    So the semantic fields of these words are coterminous.
    – bdsl
    Sep 23 '15 at 13:26

"Con-" has the meaning of :

used with certain words to add a notion similar to those conveyed by with, together, or joint congenial, congregation, console, consonant, construct, converge, etc.

It has the same meaning as "co-", which means:

together; mutually; jointly

"Conterminous" and "Coterminous" do mean the same.


Dictionary.com disagrees with the currently accepted answer. It lists "coterminous" as one of the possible meanings of "conterminous", but also two other meanings.

Its definitions of "coterminous":

  1. having the same border or covering the same area.
  2. being the same in extent; coextensive in range or scope.

Its definitions of "conterminous":

  1. having a common boundary; bordering; contiguous.
  2. meeting at the ends; without an intervening gap:
    In our calendar system, the close of one year is conterminous with the beginning of the next.
  3. coterminous.

Indeed, the National Geographic Style Guide says to use "conterminous" for the 48 contiguous states of the U.S.; that fits with definition 1 for "conterminous" and not with either of the definitions for "coterminous".

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