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Oahu Akialoa

Akialoa ellisiana

The letter "O" is the fifteenth letter and the fourth vowel in the Latin alphabet. It is used in the modern English alphabet and the alphabets of other Western European languages, as well as worldwide.

Identification Tips

In its uppercase form, "O" is a simple circle. The lowercase "o" is a smaller, but still circular shape. Both forms have remained consistent in design from Phoenician times to the present.


The letter "O" traces its origins back to the Phoenician letter 'ayin, which represented an eye and was drawn as such. Its sound value was that of a consonant, likely [ʕ]. The Greeks adapted it for the vowel sound /o/, and it was passed down to the Old Italic alphabets, including early Latin. The Greek alphabet later introduced a variation, Omega, to distinguish the long "O" sound from the short "O" sound of Omicron.

Use in Writing Systems

In English, "O" can represent a variety of sounds, including the "long" /oʊ/ as in "boat," which is often a diphthong, and the "short" /ɒ/ as in "fox." It can also represent /uː/ or /ʊ/ in digraphs like "oo," or the diphthong /ɔɪ/ in "oi" or "oy." In other contexts, it may represent /ʌ/, as in "son," or the semivowel /w/ as in "choir."

Other Languages

"O" is associated with open-mid back rounded vowel [ɔ], mid back rounded vowel [o̞], or close-mid back rounded vowel [o] in many languages. It can also represent various back vowels that are at least partly open.

Other Systems

In the International Phonetic Alphabet, "O" represents the close-mid back rounded vowel.

Related Characters

Descendants and related characters in the Latin alphabet include various forms of "O" with diacritics, such as "Ö" and "Ø," which are used to represent sounds not present in the original Latin and Greek alphabets.

Other Representations

In computing, "O" has specific Unicode and ASCII codes. It is also represented in Morse code, signal flags, semaphore, manual alphabets, and Braille.

See Also

The letter "O" is sometimes confused with the number zero due to their similar appearance in some typefaces. It is important to distinguish between the two, especially in contexts where both letters and numbers are used.

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A photo of a Lesser Redpoll (Acanthis cabaret) , male

Lesser Redpoll

Acanthis cabaret
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What Our Birders Say
Stewart W
Fantastic to be involved
Fantastic to be involved, great for mental health and gets you responding with the Challenges that are to takd part in.
A mordern game changer
Birda is an awesome app, its updated the world of birding to the modern day with a fun and easy to use app. It’s engaging and allows positive interaction with fellow bird lovers!
Great app for learning Birds
I’ve been using the app for a couple of months and love it....Someone said it’s like a real life Pokémon Go for birds. They’re not far off! It’s something that the family can do that gets you out and about. Well worth downloading no matter your age.
Louise L
Easy to use and accurate
Love this app. It is easy to use and accurate, Their backup communication is really good. I noted a missing species. All through the process, I was kept informed about the progress in correcting the information. I now have the corrected, updated version. 😁 Thanks!
A Friendly Place
I love using the bird app, I have a pretty good knowledge of birds. But I do have some gaps in it, so it’s nice to have a safe space to check on a sighting to confirm the species. It’s really enjoyable and I love the badges you can collect. It’s like a real life Pokémon go.
Alex J
Friendly and helps to identify birds
Great birding app, good for logging your sightings, also has nice species guide. I'm enjoying the social aspect more than I expected, everyone seems friendly and helps to identify unknown birds. Good mix of newbies and experienced users.
Alice J
Awesome Birding Community
I absolutely love the community aspect of this app. The app is so user friendly and has fun interactive challenges to get you out birding. I’ve tried others but since I’ve started using Birda I’ve not gone back!
Awesome App
I really enjoy using this app! It is such a friendly community of bird-lovers who are happy to help if I need ID advice. It’s been great motivation to get outdoors and go birding more! 10/10 😍😍
Talli A
My favourite app
As a young birdwatcher who was always keen to be apart of a community but never seemed to find one, my problem was solved downloading this!!! Everyone is so friendly and just as excited to see birds as me 😁
Love Birda
I love this app. It really encourages you to log your sightings and the community is friendly and helpful.
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