West Frisian phonology

/v/ has two allophones: an approximant [ʋ], which appears word-initially, and a fricative [v], which occurs elsewhere.[12]

The distinction between /ɡ/ and /ɣ/ is very marginal, and the two 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, while the fricative [ɣ] occurs elsewhere.[13][14] However, there are some cases that disturb this distribution, showing that the allophony is not purely due to stress but also has a morphological factor:

• Compound words preserve each allophone of the individual words intact, e.g. berchgeit [ˈbɛrɣɡait] "mountain goat" and needgefal [ˈneːdɡəfɔl] "emergency". These cases demonstrate plosive [ɡ] before unstressed syllables.
• Some suffixes draw the stress onto themselves, without readjusting the allophones, e.g. hartoch [ˈhatɔχ] "duke" → hartoginne [hatɔˈɣɪnə] "duchess". This 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, this representation follows the above rule of allophony, but in words with multiple morphemes the underlying status (plosive or fricative) must be known in order to recover the correct pronunciation.

Schwa /ə/ is often dropped in the combination /ən/, turning the /n/ into a syllabic sonorant. The specific sonorant that arises depends on the preceding consonant so that it is labial [m̩] when preceded by labial [m, p, b], alveolar [n̩] when preceded by labiodental or alveolar /f, v, n, t, d, s, z, r, l/ and velar [ŋ̍] when preceded by velar /k, ɣ/.[15]

Schwa is also commonly dropped in /əl/ and /ər/, creating the syllabic sonorants [l̩] and [r̩], respectively. There are also some other cases.[15]

The sequences /nj, tj, sj, zj/ coalesce to [ɲ, tɕ, ɕ, ʑ].

West Frisian has final obstruent devoicing, meaning that voiced obstruents are merged with the voiceless ones at the end of a word. Thus, word-final /b, d, v, z, ɣ/ are merged into voiceless /p, t, f, s, χ/, although final /b/ is rare.[16] The spelling reflects this in the case of the fricatives, but not in the case of the plosives, which remain spelled with ⟨b⟩ and ⟨d⟩.

• The long vowels are considerably longer than the short vowels. The former are generally over 250 ms, whereas the latter are generally under 150 ms.[19][20]
• Some speakers merge the long vowels /iː, uː/ with the centering diphthongs /iə, uə/.[21]
• /yː/ is infrequent.[22] It and the other long close rounded vowel /uː/ are absent from the dialect of Leeuwarden.[23]
• /ø/ is phonetically central [ɵ] and is quite similar to /ə/. It can be treated as its stressed equivalent.[24][25] In phonemic transcription, many scholars[26] transcribe it with ⟨ø⟩, but ⟨ɵ⟩ and ⟨ʏ⟩ are occasionally also used.[27]
• Although they pattern with monophthongs, the long close-mid vowels transcribed /eː, øː, oː/ are often realized as narrow closing diphthongs [ei, øy, ou].[28][29] However, there are exceptions: for instance, speakers of the Hindeloopers dialect realize /øː/ as a long monophthong [øː].[23]
• Nearly all words with /øː/ are loanwords from Standard Dutch.[30]
• /oː/ doesn't occur before /s/.[13]
• Although they pattern with monophthongs, the long open-mid vowels transcribed /ɛː, ɔː/ tend to be realized as centering diphthongs [ɛə, ɔə].[31][32]
• The Hindeloopers and Súdwesthoeksk dialects also feature open-mid front rounded vowels /œ, œː/, which are not a part of the standard language.[23][33]
• Many scholars[26] transcribe /a/ as /a/, but de Haan (2010) transcribes it as /ɑ/.[34] Its phonetic quality has been variously described as central [ä][19] and back [ɑ].[34]
• /aː/ is central [äː].[34][19]

• In Southwestern dialects, the sequences /wa, wo/ are monophthongized to short central [ɞ, ɵ].[35]
• The closeness of either of the elements of /ɛi/ is somewhat variable, so that its phonetic realization is [æi ~ æɪ ~ ɛi ~ ɛɪ].[36]
• The first element of /œy/ is more like [œ] than [ø].[36] Many scholars[37] transcribe this sound as /øy/, Booij (1989) transcribes it as /ʌy/, yet this article transcribes it /œy/ to show that it is clearly distinct from the common diphthongal realization of /øː/ (having a much lower starting point) and that it is virtually identical to /œy/ in Standard Dutch.
• Some scholars[38] transcribe /ɔu/ as /ɔu/, yet others[39] transcribe it as /au/. Phonetically, the first element of this diphthong may be either of these, i.e. [ɔ] or, less often, [a].[40]
• Some varieties realize /ai/ as [ɔi].[17] It is replaced by /ɛi/ in the Wood Frisian dialects.
• Many speakers realise /aːj/ as rounded /ɔːj/.[36]

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.[41] This view is supported by Hoekstra & Tiersma (2013) who transcribe them with consonant symbols /jɪ, jɛ, wa, wo/,[42] which is the convention 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 these sequences, because it is shifted entirely to the next syllable when a following vowel is added. Visser[43] also includes sequences of a high vowel plus glide among these. Such sequences are transcribed with a consonant symbol in this article, e.g.

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

Some falling diphthongs alternate with the rising ones:[17]

• The /yə/ - /jø/ alternation occurs only in the pair mentioned above.[17]