West Frisian phonology

/v/ has two allophones: an approximant [ʋ], which appears word-initially, and a fricative [v], which occurs elsewhere.[13]

The distinction between /ɡ/ and /ɣ/ is very marginal, and they are generally considered allophones of a single phoneme. The plosive [ɡ] generally appears at the beginning of a word and at the beginning of a stressed syllable, with the fricative [ɣ] occurring elsewhere.[14][15] However, there are some cases that disturb that distribution, which shows that the allophony is not only caused by stress but also has a morphological factor:

• Compound words preserve intact each allophone of the individual words: berchgeit [ˈbɛrɣɡait] "mountain goat" and needgefal [ˈneːdɡəfɔl] "emergency". That demonstrates plosive [ɡ] before unstressed syllables.
• Some suffixes draw the stress onto themselves without readjusting the allophones: hartoch [ˈhatɔχ] "duke" → hartoginne [hatɔˈɣɪnə] "duchess". That creates cases of fricative [ɣ] before stressed syllables.

Thus, it appears that the underlying representation of words includes the plosive-fricative distinction. In single-morpheme words, that representation follows the above rule of allophony, but in words with multiple morphemes the underlying status (plosive or fricative) must be known to recover the correct pronunciation.

The schwa /ə/ is often dropped in the combination /ən/, which turns the /n/ into a syllabic sonorant. The specific sonorant that arises depends on the preceding consonant and so it is labial [m̩] when it is preceded by labial [m, p, b], alveolar [n̩] when it is preceded by labiodental or alveolar /f, v, n, t, d, s, z, r, l/, and velar [ŋ̍] when preceded by velar /k, ɣ/.[16]

The schwa is commonly dropped also in /əl/ and /ər/, creating the syllabic sonorants [l̩] and [r̩], respectively. There are also some other cases.[16]

The sequences /nj, sj, zj/ coalesce to [ɲ, ɕ, ʑ], unless /j/ occurs as a part of the rising diphthongs /jɪ, jɛ, jø/.

West Frisian has final obstruent devoicing and so voiced obstruents are merged with the voiceless obstruents at the end of words. Thus, word-final /b, d, v, z, ɣ/ are merged into voiceless /p, t, f, s, χ/, although final /b/ is rare.[17] The spelling reflects that in the case of the fricatives but not in the case of the plosives, which are still written ⟨b⟩ and ⟨d⟩.

• The long vowels are considerably longer than the short vowels. The former are generally over 250 ms, and the latter are generally under 150 ms.[20][21]
• Some speakers merge the long vowels /iː, uː/ with the centering diphthongs /iə, uə/.[22]
• /yː/ is infrequent.[23] It and the other long close rounded vowel /uː/ are absent in the Leeuwarden dialect.[24]
• /ø/ is phonetically central [ɵ] and is quite similar to /ə/. It can be treated as its stressed equivalent.[25][26] In phonemic transcription, many scholars[27] transcribe it with ⟨ø⟩, but ⟨ɵ⟩ and ⟨ʏ⟩ are occasionally used.[28]
• Although they pattern with monophthongs, the long close-mid vowels transcribed /eː, øː, oː/ are often realized as narrow closing diphthongs [ei, øy, ou].[29][30] However, there are exceptions: for instance, speakers of the Hindeloopers dialect realize /øː/ as a long monophthong [øː].[24] Nearly all words with /øː/ are loanwords from Standard Dutch.[31]
• /oː/ does not occur before /s/.[14]
• Although they pattern with monophthongs, the long open-mid vowels transcribed /ɛː, ɔː/ tend to be realized as centring diphthongs [ɛə, ɔə].[32][33]
• The Hindeloopers and the Súdwesthoeksk dialects also feature open-mid front rounded vowels /œ, œː/, which are not a part of the standard language.[24][34]
• Many scholars[27] transcribe /a/ with ⟨a⟩, but de Haan (2010) transcribes it with ⟨ɑ⟩, following the usual transcription of the short open vowel in Dutch.[35] Its phonetic quality has been variously described as central [ä][20] and back [ɑ].[35]
• /aː/ is central [äː].[35][20]

• In southwestern dialects, the sequences /wa, wo/ are monophthongized to short central [ɞ, ɵ].[36]
• The closeness of both elements of /ɛi/ is somewhat variable and so its phonetic realization is [æi ~ æɪ ~ ɛi ~ ɛɪ].[37]
• The first element of /œy/ is more like [œ] than [ø].[37] Many scholars[38] transcribe the sound as /øy/, Booij (1989) transcribes it as /ʌy/, but this article transcribes it /œy/ to show that it is clearly distinct from the common diphthongal realization of /øː/ since it has a much lower starting point), and it is virtually identical to /œy/ in Standard Dutch.
• Some scholars[39] transcribe /ɔu/ as /ɔu/, but others[40] transcribe it as /au/. Phonetically, the first element of the diphthong may be either [ɔ] or less often [a].[41]
• Some varieties realize /ai/ as [ɔi].[18] It is replaced by /ɛi/ in the Wood Frisian dialects.
• Many speakers realise /aːj/ as rounded /ɔːj/.[37]

Frisian is traditionally analysed as having both falling and rising diphthongs. Booij (1989) argues that the rising diphthongs are in fact glide-vowel sequences, not real diphthongs.[42] That view is supported by Hoekstra & Tiersma (2013) who transcribe them with consonant symbols /jɪ, jɛ, wa, wo/,[43] which is the convention that is used in this article.

Frisian also possesses sequences of a long vowel followed by a glide. According to Booij, the glide behaves as a consonant in such sequences since it is shifted entirely to the next syllable when a following vowel is added. Visser[44] also includes sequences of a high vowel plus glide among these. Such sequences are transcribed with a consonant symbol in this article:

• aai /aːj/ ~ aaien /ˈaː.jən/
• bliuw /bljoːw/ ~ bliuwen /ˈbljoː.wən/
• moai /moːj/ ~ moaie /ˈmoː.jə/
• iuw /iːw/ ~ iuwen /ˈiː.wən/
• bloei /bluːj/ ~ bloeie /ˈbluː.jə/

Some falling diphthongs alternate with rising diphthongs:[18]

• The /yə/ - /jø/ alternation occurs only in the pair mentioned above.[18]