Dadanitic [formerly called 'Dedanite' and 'Lihyanite'] was the alphabet used by the inhabitants of the ancient oasis of Dadan (Biblical Dedān, modern al-ʿUlā in north-west Saudi Arabia), probably some time during the second half of the first millennium BC. Dadan was an important centre on the caravan route bringing frankincense from ancient South Arabia to Egypt, the Levant and the Mediterranean. Dadanitic has the same repertoire of 28 phonemes as Arabic and is the only ancient member of the South Semitic script family to use matres lectionis (i.e. some letters — h, w, and y — to represent both consonants and vowels or, in the case of y a diphthong). It was used for both monumental inscriptions and graffiti. The fact that many of the letters developed informal shapes, at the same time as the formal ones were being used — we can see both shapes in the same inscriptions — strongly suggests that the script was being used extensively to write in ink. This is because changing the shape of a letter is of no help to someone who only carves on stone. It is only when one is writing in ink that pressures of speed and ease provide the impetus for developing letter forms to make them easier and quicker to write. These new forms are then sometimes transferred to stone. Dadanitic inscriptions and graffiti are mainly concentrated in the oasis of al-ʿUlā and the mountains surrounding it, with a few distributed more widely.