The phonology of Welsh is characterised by a number of sounds that do not occur in English and are rare in European languages, such as the voiceless alveolar lateral fricative [?] and several voiceless sonorants (nasals and liquids), some of which result from consonant mutation. Stress usually falls on the penultimate syllable in polysyllabic words, while the word-final unstressed syllable receives a higher pitch than the stressed syllable.
Symbols in parentheses are either allophones, or found only in loanwords. The sound /z/ generally occurs in loanwords, e.g. sw /zu:/ ('zoo'), although this is usually realised as /s/ in northern accents, e.g. /su:/. The postalveolar affricates /t?/ and /d?/ occur mainly in loanwords, e.g. tsips /tps/ ('chips') and jeli /'dli/ ('jelly'), but also in some dialects as developments from /tj/ and /dj/, e.g. /d?aul/ from diafol /'djav?l/ ('devil'). The voiceless nasals /m? n? / occur mostly word-initially, as a consequence of nasal mutation. Initial /?w/ (or //) is colloquially realised as [?] in the south, e.g. chwech /?we:?/ ('six') pronounced [?e:?].
[ç] results from /j/ when preceded by /h/, often as a result of h-prothesis of the radical word, e.g. iaith /jai/ 'language' becomes ei hiaith [?i çai] 'her language'. It also occurs in some Northern dialects as the cluster /çj/ in place of intervocalic /?/ in words like allan ('out') where it is pronounced [açjan] rather than the more common (and standard) [a?an].
The stops /p t k/ are distinguished from /b d ?/ by means of aspiration more consistently than by voicing, as /b d ?/ are actually devoiced in most contexts. This devoiced nature is recognised in the spelling of /sp sk/ as ⟨sb sg⟩, although /st/ is orthographically ⟨st⟩ for historical reasons.
The fricatives /v ð/ may also be devoiced in some contexts, but are distinguished from /f ?/ by having a shorter frication length than the latter. There is a tendency in the spoken language not to pronounce these voiced fricatives in certain contexts, e.g. nesaf /n?sav/ ('next') realised as /'n?sa/ or i fyny /i: 'v?n?/ ('up') from mynydd /m?n?ð, m?n?ð/ ('mountain'). Historically, this occurred so often with the voiced velar fricative that it disappeared entirely from the language. Some speakers realise the voiceless lateral fricative /?/ as a voiceless palatal fricative [ç] in some or all contexts. The occurrence and distribution of the phoneme /?/ varies from area to area. Very few native words are pronounced with /?/ by all speakers, e.g. siarad /'?arad/ ('talk'), although it appears in borrowings, e.g. siop /p/ ('shop'). In northern accents, it can occur when /s/ precedes /i: j/ or /j/, e.g. mi es i /mi 'e:? i:/ ('I went'). In some southern dialects it is produced when /s/ follows /?/ or /i:/, e.g. mis /mi:?/ ('month'). The voiceless fricative /?/ is realised as uvular except by some southwestern speakers, who produce the sound in the velar region as [x].
In northern Welsh, the alveolar lateral approximant is consistently velarised or "dark" in all positions, but remains unvelarised or "clear" in the south, except in rare exceptions where the Dark L is found after /d/ in dlos 'pretty'.
The vowel phonemes of Welsh are as follows:
The vowels /?/ and /?:/ survive from Old Welsh only in northern dialects; in southern dialects, these vowels have become /?/ and /i:/ respectively. In all dialects, the contrast between long and short vowels is found in stressed word-final syllables (mainly monosyllabic words), whereas in some southern dialects, the contrast is found in stressed non-word-final syllables in addition.
The long counterpart to short /a/ is sometimes misleadingly transcribed /?/. This is often found in solely quality-distinctive transcriptions to avoid using a length mark. The actual pronunciation of long /a/ is [a:], which makes the vowel pair unique in that there is no significant quality difference. Regional realisations of /a:/ may be [æ:] or [?:] in north-central and (decreasingly) south-eastern Wales or sporadically as [?:] in some southern areas undoubtedly under the influence of English.
|mid||?i/?i, ?i||/,||?u/?u, ?u|
The diphthongs containing /?/ occur only in northern dialects; in southern dialects // is replaced by /?i/, /?u, ~, / are merged with /?u, ?i~?i, ?i/, and /a?, a:?/ are merged with /ai/. There is a general tendency in the South to simplify diphthongs in everyday speech, e.g. Northern /?wa:/ corresponding to /?wa:?/ in the South, or Northern /?w?i?j?/ and Southern /?wi/.
Stress in polysyllabic words occurs most commonly on the penultimate syllable, more rarely on the final syllable (e.g. verbs ending in -áu). Exceptions can arise in relation to borrowings from foreign words, such as ambiwlans and testament (both stressed on the first syllable). According to its positioning, related words or concepts (or even plurals) can sound quite different, as syllables are added to the end of a word and the stress moves correspondingly:
Note also how adding a syllable to ysgrifennydd to form ysgrifenyddes changes the pronunciation of the second ⟨y⟩. This is because the pronunciation of ⟨y⟩ depends on whether or not it is in the final syllable.
Stress on penultimate syllables is characterised by a low pitch, which is followed by a high pitch on the (unstressed) word-final syllable. In words where stress is on the final syllable, that syllable also bears the high pitch. This high pitch is a remnant of the high-pitched word-final stress of early Old Welsh (derived from original penultimate stress in Common Brittonic by the loss of final syllables); the stress shift from final to penultimate occurred in the Old Welsh period without affecting the overall pitch of the word.