[1] It is used in various languages, including Persian, Arabic (as أستاذ ’ustāḏ), Azerbaijani, Urdu, Hindi, Bengali, Marathi, Dhivehi, Punjabi, Pashto, Turkish, Kazakh, Uzbek, Indonesian, Malay and Kurdish.
Ustad is only used for qualified Islamic scholars in Brunei, Indonesia, Malaysia, the Philippines, Singapore, Southern Thailand where it is a direct equivalent of terms such as shaykh in the Arab world, and mawlānā in the Indian Subcontinent.
and from Persian استاد) is an honorific title for an expert person in Indian classical singing and instrumental playing, used for a Muslim musician.
The title is awarded to musicians by their teachers, prominent individuals, or members of their gharana in recognition of their expertise.
As they are informal titles, mentioning the names of eminent singers without those appendages is acceptable, unlike prefixes like doctor awarded formally by educational institutions.