Shortening of long vowels in unstressed syllables occurs irregularly. Long vowels also occur in unstressed syllables. Russian has vowel reduction in unstressed syllables. This produced many lexical and grammatical alternations between stressed and unstressed syllables. Schwa is a short vowel which vanishes to nothing at unstressed position. Like Catalan and German, Portuguese uses vowel quality to contrast stressed syllables with unstressed syllables. Stressed syllables are louder and longer than unstressed ones. Vulgar Latin had five vowels in unstressed syllables&colon; . The Sami languages have a trochaic pattern of alternating stressed and unstressed syllables. It thus commonly occurs before unstressed syllables. Some unstressed short vowels have been elided. Most Coptic dialects have two phonemic vowels in unstressed position. Both occurred in stressed and unstressed syllables. That caused a steady erosion of vowels in unstressed syllables. In most dialects of Russian unstressed and reduce to either or schwa.