One unresolved question in Gaelic orthography involves whether or not to represent compensatory lengthening directly in the spelling of words.

  1. -ll, -nn, -rr, -m
  2. -rd, -rn, -rl

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1. -ll, -nn, -rr, -m

There is a general rule in Gaelic phonology that a short vowel in a stressed syllable is lengthened / diphthongised before a fortis sonorant which is immediately followed by either a consonant or a word boundary.

Here are some examples of words where this compensatory lengthening occurs:



fionn, ionnsaich
grunn, grunnd
tiurr, sgurr
cum, ciurrte
buill, uillt
cluinn, gruinnd

foill, boillsg



ceann, beanntan
gearr, bearrte
ball, allt
bann, sannt
cam, am, lampa
fainn, cainnt
maim, Caimbeul

Note that compensatory lengthening does not occur when the sonorant is immediately followed by a vowel, for example in sealladh, beinne, toman, or cluinnidh. Note also that a few words actually have "inherent" diphthongs or long vowels before fortis sonorants. You can distinguish these by the fact that the vowel stays the same, even when followed by a vowel, e.g. ciall / ciallachadh, ceum / ceumannan, fèill / fèille.

Note also the following exception, where compensatory lengthening does happen despite a following vowel - ceannard. According to Blas na Gàidhlig, this word is, at an underlying level, something like ceannphort.

Here is what GOC (2009) has to say about how to represent compensatory lengthening in orthography -
  • "4f - In the case of spelling of diphthongs with m in words such as: cam, lampa, lom, trom the spelling without the accent should be retained except in: àm (time) which should have an accent to differentiate it from other words spelt am."
  • "4i - The conventional spelling without an accent should be retained on the long vowel sound before ll and nn in words such as: cinnteach, fillte, inntinn, till, bonn, cunntas, sanntach. This principle should also be applied to words formerly spelt with the accent, e.g. dilleachdan, dinnear, trilleachan."

Aside from the nonsensical last sentence, this can be read as saying the following - Compensatory lengthening before a fortis sonorant should not be explicitly represented in orthography by use of an accent (apart from the case of àm). There are some very good reasons for this. Firstly, it allows the root morpheme to be orthographically consistent (compare seall / sealladh versus *seàll / sealladh, or tom / toman versus *tòm / toman). Secondly, it means that there is a clear orthographic distinction between inherently long vowels and compensatory-lengthened ones. [Question - Is the vowel in màm a long vowel of a diphthong? Are there any such contrasts?]

Note however that GOC only talks about vowels before -m, -ll and -nn, and ignores the question of what to do before -rr. However, the GOC wordlist appendix does contain the following examples:
  • feàrr, deàrrsach, geàrr-chunntas, meàrrsadh

This has been interpreted as an implicit GOC recommendation that compensatory lengthening before -rr should be explicitly represented in orthography by means of a grave accent, with morphologically related pairs like bàrr / barran, geàrr / gearradh, etc.

Critics of GOC argue that there is an inconsistency in these recommendations - compensatory lengthening should be explicitly represented by an accent in some contexts but not in others. However, there might be another sense in which GOC is arguably not being inconsistent here - the implicit principle is "always represent compensatory lengthening explicitly with an accent, unless there is some good reason not to do so, for example if the lengthening results in a surface diphthong rather than a normal long vowel".

Note also that the GOC wordlist specifies the spelling rùm for some reason.

2. -rd, -rn, -rl

There is a general rule in Gaelic phonology that a short vowel in a stressed syllable is lengthened before an -rd, -rn or -rl cluster. This happens across the board, even if the cluster is immediately followed by a vowel.

GOC gives no explicit guidance on whether to use an accent here or not. If the general principle is to avoid accents when they are redundant, then no accent should be used. However, if the general principle is to represent surface lengthening explicitly unless there is a good reason not to, then an accent should be used. Inducing from the GOC wordlist, the implicit recommendation in GOC is for the latter approach:
  • àird, àirneis, àirleas, eàrlas, àrd, beàrn, Beàrnaraigh, ceàird, ceàrd, ceàrn, ceàrnaidh, ceàrnag, ceàrnagach, còrnair, gàrlach, geàrd, làrna-mhàireach, òirleach, òrdaich, òrdugh, teàrn, ùrlar, ùrnaigh.

Check out section 5.6.2 of Blas na Gàidhlig for more information.

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