Conventionally the word "sufi" is considered synonymous with the word "mystic". But the word "sufi", as used in Arabic, Persian, Turkish and Urdu, has a religious connotation. According to the Sufis themselves, the word is derived from an Arabic root "safa" (purity). They opine the sufi is he who keeps his heart pure with God. According to another connotation the word 'sufi' is apparently derived from an Arabic word suf meaning coarse wool and was originally applied to those Muslim mystics who wore coarse woollen garments as a _sign of self renunciation and penitence.