Written Scottish Gaelic uses the Roman alphabet, and includes the consonants b, c, d, f, g, h, l, m, n, p, r, s, and t and the vowels a, e, i, o, and u. Grave accent marks are used to denote long vowels, while acute accents were used in older texts (but have been abandoned in modern writing) to differentiate different qualities of 'e' and 'o.'
Some general principles for reading Scottish Gaelic orthography are addressed below; however, be aware that there are many exceptions to the following 'rules.' For a more detailed treatment, see the website http://www.akerbeltz.org/fuaimean/fuaimean.htm, a very thorough and accessible reference which includes rules, word lists, and corresponding sound files.
Consonants in Scottish Gaelic are classified as either 'broad' (leathann, sometimes referred to as 'plain' or 'velarized') or 'slender' (caol, sometimes referred to as 'palatalized')
Orthographically, vowels are also classified as broad or slender. The graphemes 'a,' 'o,' and 'u' are broad, while 'i' and 'e' are slender.
Vowels on both sides of a consonant must agree with its broad/slender quality, allowing the reader to determine consonant quality directly from the orthography. The traditional mnemonic for remembering this is Caol ri caol is leathann ri leathann (slender with slender and broad with broad). In order to read a word, the reader must separate the vowels which are only there as a guide to the pronunciation of the consonant from those which are pronounced.
Broad stops generally correspond to their English equivalents, while the slender versions are palatalized (see Sounds of Scottish Gaelic for further details). What appears from the orthography to be a voicing distinction (i.e. 'b' vs. 'p') is actually a distinction in aspiration (the grapheme 'b' corresponds to [p], while 'p' is [pʰ].
Fricatives are indicated by sequences o two consonants, always ending in 'h.' Exceptions are 's' and 'f,' which are spelled the same way as English. Again, whether the fricative is broad or slender is indicated by the surrounding vowel(s):
Broad Slender ph [f] ph [fʲ] bh [v] bh [vʲ] mh [v] mh [vʲ] ch [x] ch [ç] dh [ɣ] dh [ʝ] gh [ɣ] gh [ʝ] th [h] th [h] sh [h] sh [h] fh silent fh silent (n.b. in a small number of words, 'fh' is pronounced [h]
Lenition is indicated by an 'h' following the lenited consonant for all lenitable consonants except 'l,' 'n,' and 'r.'
Liquids are always tense word-initially. Double letters (ll, nn, rr) which occur intervocalically represent historic tense consonants. However, modern pronunciation does not necessarily correspond with this.
Long vowels are indicated by a grave accent (à, è, ì, ò, ù). When a vowel has an accent mark, that vowel is pronounced, and any adjacent vowels are used for determining the broadness/slenderness of neighboring consonants.
An acute accent is used on 'e' and 'o' (é, ó) in older texts to indicate a slightly different vowel quality. The distinction still exists, although some dialects may be losing it (Gillies 1993); however, this distinction is no indicated by the orthography.
Hiatus is often indicated by a silent 'bh,' 'mh,' 'dh,' 'gh,' or occasionally 'th' between two vowels.
In closed, unstressed syllables, short vowels are pronounced [ə] (or [ɪ]), and long vowels and dipthongs are pronounced [a]. In open unstressed syllables, [i] and [u] can also occur.
Vowel lengthening occurs on short vowels preceding ‘rr,’ ‘ll,’ ‘nn,’ and ‘m’ in all positions EXCEPT when there is also a vowel following the consonant. The vowel either becomes long or a diphthong. The contrast is sometimes, but not always, indicated in the orthography.
Below is a chart of graphemes with corresponding options for the pronunciation of vowels and dipthongs in IPA. While these are the most common options, keep in mind that there are exceptions.
a [a], [au] e [e] i [i] o [o], [[ɔ], [ɔu] u [u] ai [a], [ai], [ɯi] ea [ɛ], [e], [a], [au] ia [iə] oi [ɔ], [ɤ] ua [uə] ao [ɯ:] ei [ɛ], [ei] io [i] ui [u] aoi [ɯ:]/ [ɯi] eo [ɔ] iu [u] uai [uə] adh, agh [ɤ(:)] eu [ia], [e:] iai [iə] abh, amh [au]