Some languages allow other sounds to form the nucleus of a syllable, such as the syllabic (i.e., vocalic) l in the English word table (when not considered to have a weak vowel sound: ) or the syllabic r in the Serbo-Croatian word vrt "garden".

The phonetic definition of "vowel" (i.e. a sound produced with no constriction in the vocal tract) does not always match the phonological definition (i.e. a sound that forms the peak of a syllable). The approximants