"There are only four feet between them."
Translation:Níl ach ceithre throigh eatarthu.
Why is the singular throigh used in this example, but the plural throithe in the ar fád example?
The full set of nouns that use a plural form following some numbers can be found in the 2012 Caighdeán, §9.3.2, page 159 — viz bliain, ceann, cloigeann, fiche, pingin, seachtain, trian, troigh, and uair. (Bliain, fiche, pingin, seachtain, trian, and uair use different plural forms after numbers than their usual plural forms.) For these nouns, one and two use a lenited singular (as usual), three through six use an unmutated plural instead of a lenited singular, and seven through ten use an eclipsed plural instead of an eclipsed singular. Uair, the only one of these nouns that begins with a vowel, gets a prefixed h following trí, ceithre, and sé. These same rules apply for 11 through 19 (modulo 10). Numbers 110 and higher that leave a remainder of ten when divided by 100 use the same rule as ten above; other numbers 20 and higher that are evenly divisible by ten use an unmutated singular (as usual); and numbers 21 and higher that aren’t evenly divisible by ten use the same rules (modulo 10) as one through nine above.
EDIT: The rules are also in the 2016 and 2017 editions of the Caighdeán (§9.3.2, page 146).
Thank you both for the details! So ... Níl ach ceithre troithe eatharthu. should be correct in this example?
Can one find the English translation of the caighdeán if so where thank you
An Caighdeán Oifigúil (http://www.oireachtas.ie/parliament/about/rannoganaistriuchain/ancaighdeanoifigiuil/) is only made available in Irish. I'm not aware of an English translation.
(I see that the 2017 edition is now available at that link. I haven't had time to see what changes have been introduced).
Three years ago, it was suggested that "Níl ach ceithre troithe eatharthu." is correct. If this is the case, please correct the accepted translation.