The most characteristic feature of the Punjabi language is its tone system. The script has no separate symbol for tones, but they correspond to the tonal consonants that once represented voiced aspirates as well as older *"h". To differentiate between consonants, the Punjabi tonal consonants of the fourth column, ਘ "kà", ਝ "chà", ਢ "ṭà", ਧ "tà", and ਭ "pà", are often transliterated in the way of the voiced aspirate consonants "gha", "jha", "ḍha", "dha", and "bha" respectively, although Punjabi lacks these sounds. Tones in Punjabi can be either rising, neutral, or falling; in the pronunciation of the names of the Gurmukhī letters, they are at the beginning of the word and as such produce the falling tone, hence the grave accent (à) as opposed to the acute. The tone on the stem vowel changes to a rising one (á) and precedes the letter when it is in syllabic coda positions, and is falling when the letter in stem-medial positions after a short vowel and before a long vowel, and when the tonal letter follows the stem vowel. The letters now always represent unaspirated consonants, and are unvoiced in initial positions and voiced elsewhere.