O
⟨o′⟩, in the practical orthography of the Taa language, represents the glottalized or creaky vowel /o̰/. It is also used for and in Romanized Uzbek (Cyrillic ⟨ў⟩). Technically it is not a digraph in Uzbek, since ⟨ʻ⟩ is not a letter of the Uzbek alphabet, but rather a typographic convention for a diacritic. In handwriting the letter is written ⟨ō⟩ or ⟨ŏ⟩.
⟨oa⟩ is used in English, where it commonly represents the /oʊ/ sound as in road, coal, boast, coaxing, etc.. In Middle English, where the digraph originated, it represented /ɔː/, a pronunciation retained in the word broad and derivatives, and when the digraph is followed by an "r", as in soar and bezoar. The letters also represent two vowels, as in koala /oʊ.ɑː/, boas /oʊ.ə/, coaxial /oʊ.æ/, oasis /oʊ.eɪ/, and doable /uː.ə/. In Malagasy, it is occasionally used for /o/.
⟨oe⟩ is found in many languages. In English, oe represents the /oʊ/ sound as in hoe and sometimes the /uː/ sound as in shoe. Afrikaans and Dutch oe is, as in doen. In French it stands for the vowels, as in œil, and as in oesophage, and in Cantonese Pinyin it represents the vowel ~ . It is an alternative way to write the letter ö in German when this character is unavailable. In Zhuang it is used for (⟨o⟩ is used for ). In Piedmontese, it is .
⟨oê⟩ is used in French to write the vowel sound in a few words before what had historically been an s, as in poêle "stove".
⟨õe⟩ is used in Portuguese orthography for . It is used in plural forms of some words ended in ⟨ão⟩, such as anão–anões and campeão–campeões.
⟨oh⟩, in the practical orthography of the Taa language, represents the breathy or murmured vowel /o̤/.
⟨oi⟩ is used in various languages. In English, oi represents the /oɪ̯/ sound as in coin and join. In French, it represents /wa/, which was historically – and still is in some cases – written "oy." In Irish it's used for /ɛ/, /ɔ/, /ɪ/, /əi̯/, /iː/, /oː/ between a broad and a slender consonant. In Piedmontese, it is .
⟨oí⟩ is used in Irish for /iː/ between a broad and a slender consonant.
⟨oî⟩ is used in French to write /wa/ before what had historically been an s, as in boîtier or cloître.
⟨ói⟩ is used in Irish for /oː/ between a broad and a slender consonant.
⟨òi⟩ is used in Piedmontese for /oi̯/.
⟨om⟩ is used in Portuguese orthography for /õ/.
⟨ôm⟩ is used in Portuguese orthography for /õ/ before a consonant.
⟨on⟩ is used in Portuguese orthography for /õ/ before a consonant, and in French to write /ɔ̃/.
⟨ôn⟩ is used in Portuguese orthography for /õ/ before a consonant.
⟨ön⟩ is used in Tibetan Pinyin for /ø̃/. It is alternately written oin.
⟨oo⟩ is used in many languages. In English, oo commonly represents two sounds: /uː/ as in "moon" and "food", and /ʊ/ as in "wood" and "foot". Historically, both derive from the sound, which is also the digraph’s pronunciation in most other languages. In German, the digraph represents in a few words such as Moor.
⟨oq⟩, in the practical orthography of the Taa language, represents the pharyngealized vowel /oˤ/.
⟨or⟩, in Daighi tongiong pingim, represents mid central vowel /ə/ or close-mid back rounded vowel /o/ in Taiwanese Hokkien.
⟨ou⟩ is used in English for the diphthong /aʊ/, as in out /aʊt/. This spelling is generally used before consonants, with ⟨ow⟩ being used instead before vowels and at the ends of words. Occasionally ou may also represent other vowels – /ʌ/ as in trouble, /oʊ/ as in soul, /ʊ/ as in would, or /uː/ as in group. The ou in out originally represented, as in French, but its pronunciation has changed as part of the Great Vowel Shift.
In Dutch ou represents in the Netherlands or in Flanders. In French, ou represents the vowel, as in vous "you", or the approximant consonant, as in oui "yes".
This digraph stands for the close-mid back rounded vowel or for the falling diphthong, according to dialect.
⟨oû⟩ is used in French to write the vowel sound /u/ before what had historically been an s, as in soûl /sul/ "drunk".
⟨ow⟩, in English, usually represents the /aʊ/ sound as in coward, sundowner, and now or the /oʊ/ sound, as in froward, landowner, and know. An exceptional pronunciation is /ɒ/ in knowledge and rowlock. There are many English heteronyms distinguished only by the pronunciation of this digraph, like: bow (front of ship or weapon), bower (a dwelling or string player), lower (to frown or drop), mow (to grimace or cut), row (a dispute or line-up), shower (rain or presenter), sow (a pig or to seed), tower (a building or towboat).
⟨oy⟩ is found in many languages. In English and Faroese, oy represents the diphthong /ɔɪ/. Examples in English include toy and annoy.
⟨oŷ⟩ is an obsolete digraph once used in French.
⟨øy⟩ is used in Norwegian for /øʏ/.
Read more about this topic: Lj (digraph)