The triangular colon or IPA long-vowel mark is a symbol that in small fonts looks like a colon and indicates a vowel that is longer than others.
In general the triangular colon can be replaced by the normal colon.
Standard use of the triangular colon
- IPA phoneme /ɑː/, as in palm, father, bath,BrE start
- Phoneme /ɑː/ in General American, as in palm, father, start, lotAmE
- IPA phoneme /iː/, as in fleece, happy
- IPA phoneme /ɔː/, as in thought, cloth,AmE north, force
- IPA phoneme /uː/, as in goose
- IPA phoneme /ɜː/, as in nurse
Non-standard use of the triangular colon
The Concise Oxford Dictionary and Oxford Dictionaries Online use /əː/ instead of /ɜː/; This change has been referred to as having "the advantage of reducing the total number of unfamiliar symbols to be assimilated", and also "as things are, it doesn't now seem worthwhile changing what we have".
Since there are no phonemes /ɑ, i, ɔ, u/ or /ɜ/, the long-vowel mark can be suppressed with no loss of information. This is common practice in American dictionaries. On the other hand, the opposite can be done, and use /a, a:, i, i: o, o:, u/ and /u:/ instead of /a, ɑ, ɪ, i, ɒ, ɔ, ʊ/ and /u:/ (see "Reduced symbol set" in the table below):
|Standard British notation (including this website)||aɪ, aʊ||ɑː||ɪ||iː||ɒ||ɔː||ʊ||uː||ɜː|
|American notation||aɪ, aʊ||ɑ||ɪ||i||ɒ (or ɑ)||ɔ||ʊ||u||ɜ|
|Reduced symbol set||ai, au||a:||i||i:||o||o:||u||u:||ɜ:|
- Oxford Dictionaries Online, Key to pronunciations (British and World English dictionary). See əː as in her.
- Jack Windsor Lewis, IPA vowel symbols for British English in dictionaries, Section 7. /əː/ versus /ɜ:/.
- Oxford Dictionaries Online, Key to pronunciations (British and World English dictionary). See ɛː as in hair.
- Jack Windsor Lewis, IPA vowel symbols for British English in dictionaries, Section 9. /ɛː/ versus /eə/