Rabb (Arabic: رب, Turkish: Rab, Bengali: রব্ব, Hindi: रब) is an Arabic word meaning Lord, Sustainer, Cherisher, Master, Nourisher. In Islam, Ar-Rabb is often used to address Allah, although Ar-Rabb is not one of the 99 names (or attributes) of Allah. When it is used with the definite article 'Ar' (Ar-Rabb) the Arabic word refers to Allah. As for other than Allah, it can be used to say Rabb Ad-Dar, the master of such and such object or the nourisher of such and such object. Rabb is also a common and acceptable first and/or last name throughout the world.
The literal meaning of the word is Sustainer, Master and/or "Nourisher", and in that sense, a man is the "rabb" of his house. With the same root is the verb yurabbi, meaning "raise" (as in raise a child). Rabb also means "the Creator", as it is referred to in the Quran several times as "رب العالمين". However, Rabb covers such a wide meaning that other languages lack an equivalent of the word. Some have explained it to mean a fostering things in such a manner as to make them attain one condition after another until they reach their goal of completion. Thus, it conveys not only the idea of fostering, bringing up or nourishing, but also that of regulating, completing, accomplishing, cherishing, sustaining and bringing to maturity by evolution from the earliest state to that of the highest perfection. The Quran, in Surah Fatihah, introduces this name in the beginning, "All praise and gratitude is due to Allah, Rabb of all the worlds." Note that it mentions "Rabb of all the worlds", thus stating clearly that he takes care, nourishes, fosters through every stage of existence, everything that exists.
Pre-Islamic Arabians used to believe that, while there were multiple 'aalihah (gods), only Allah was the Rabb (Lord/sustainer) of the earth and heavens. He is believed to be the abstract Supreme Being who is beyond any resemblance and the one who governs the heavens and earth. In pre-Islamic Arabia, which is commonly referred to as the Jahiliya era, the worship of God(Allah) along other lesser gods was common, but Mohammad introduced a different religion centered on Allah. One of Mohammad's aims was to reintroduce Allah as being the "Rabbu alAAalameen" or "رَبِّ الْعَالَمِينَ", which translates as "the Lord of the Worlds", who is beyond being solely a creator, but also the Only Deity who should be recognized by all men. Going back in history, other prophets, such as Abraham (in the Islamic view) and Moses, were also preaching to introduce God (Allah) as the Rabb (Lord) and said:
"Surely we are the apostles of the Lord of the worlds" [26:16] "قَالَ فِرْعَوْنُ وَمَا رَبُّ الْعَالَمِينَ " which may translate as "Pharaoh said: And what is the Lord of the worlds?" [26:23] "قَالَ رَبُّ السَّمَاوَاتِ وَالْأَرْضِ وَمَا بَيْنَهُمَا ۖ إِن كُنتُم مُّوقِنِينَ" which translates as "Musa (Moses) said: The Lord of the heavens and the earth and what is between them, if you would be sure." [26:24]