Modifier Letter Low Vertical Line

It marks secondary stress: a lighter stressed syllable than the main one.

In IPA transcriptions, ˌ comes before the syllable it marks. In ˌ...ˈ..., it marks a lesser beat, while ˈ marks the word's primary, or main, stress. The pair shows two levels of prominence.

How did the IPA stress mark develop?

The IPA chart archive records a change in stress notation.

Across 1926–1930, the International Phonetic Association's chart archive shows ʹ as a general stress mark in 1926. The 1930 chart adds ˌ for secondary stress and revises ʹ to ˈ for primary stress.

Why do dictionaries use ˌ differently?

Each dictionary follows its own stress-marking convention.

Oxford's English learner's dictionary marks one or more secondary stresses before the main stress and may leave weak post-primary stresses unmarked. Merriam-Webster distinguishes secondary stress from a still weaker third level, which it leaves unmarked; the Oxford English Dictionary (OED) guide uses ˌ for its inferior stress mark. These are house-style choices, not a universal measurement.

Stress patterns differ by language, and analyses of English differ on how sharply secondary stress stands apart from unstressed speech. Fonts can draw ˌ with different heights or stroke weights, so its position in a transcription is more reliable than appearance alone.