Definition of length mark in US English:

length mark

noun

Phonetics
  • A phonetic symbol used to indicate the relative length of a vowel sound.

    ‘the vowel is either marked with a length mark or is a diphthong’
    • ‘Some phoneticians consider it preferable to treat the length mark as a mark of quantity rather than duration, and refer to 'heavy' and 'light' vowels.’
    • ‘They use such phonological notation as length marks, but they've also deviated from IPA proper to make the ads more accessible to German speakers.’
    • ‘These are traditionally divided into short and long, with a length mark, used to show that there is a difference in length as well as vowel quality.’
    • ‘The length of a vowel is usually indicated in phonetic transcription by a length mark.’
    • ‘Generally speaking, the insertion of the length mark is sufficient to render confusion impossible.’