What ː means
It lengthens the sound directly before it. In IPA, ː follows a vowel or consonant: aː marks a long vowel, while pː marks a long consonant. It records duration, not a second sound or a pause.
The mark appears in the first published IPA alphabet (August–September 1888), developed by the Phonetic Teachers’ Association to help teach pronunciation. In 1899, examples such as diːsər and fliːsər use it to mark long vowels. Later IPA charts pair ː with ˑ for full and half length. Depending on the transcription, length can mark a contrast between words or record an observed stretch.
Can I use a normal colon instead of ː?
Use ː for IPA; a plain colon is only a fallback. Some printed pronunciation guides use : when they cannot set the proper mark. In digital text, : and ː are separate characters, so substituting one for the other changes the text.
Technical notation for phonetic transcription; it reads as an instruction about speech sounds, not conversational punctuation.
A regular colon may resemble it in print, but it is a different character.
Don't confuse it with
3Combination ideas
3Questions people ask
1Why does ː sometimes look like a colon or touch nearby letters?
It depends on the typeface: colon-like signs can have round or triangular dots, and tight spacing can crowd nearby letters. A 2022 Noto Sans/Serif issue documented overlap involving ː.
How to type ː
ː\02D0Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.