Rajah or Raja is a Punjabi, Hindi, Urdu word once used exclusively as a royal title. The word "raja" may be compared with the words "king" or "monarch" (rule by one). Raja (Sanskrit rĝjan-) was the title of a princely ruler from the Kshatriya / Rajput lineages. The title has a long history in the Indian subcontinent and Southeast Asia, being attested from the Rigveda. It is now used used as a common name in India and Southeast Asia.
On Bandi Chhorh Divas Sikhs celebrate the release of Guru Hargobind from Gwalior Fort who cleverly outwitted Jahangir to also win the release of 52 Hindu Rajas (here meaning Princes). Normally the words Shezada or Sahibzada would be used to translate Prince in Persia and the Punjab by Muslims or Sikhs while Rajkumar or just Kumar would be used in Hindi, but the Mughals having an Emperor allowed the relegated the word to Princely status as did the later British Raj (the Princely States).
During the reign of Maharaja Ranjit Singh the leaders of the Sikh misls were also reduced to the rank of princes by granting the title of Maha (great) Raja to their once equal tribal chieftain or Misaldar.
The Sanskrit word rĝjan- is an n-stem, with nominative rĝjĝ. It is cognate to Latin rēx, the Gaulish rīx etc. (originally denoting tribal chiefs or heads of small 'city states'), ultimately a vrddhi derivation from a PIE root *h₃reǵ- "to straighten, to order, to rule".
Rather common variants in Hindi, used for the same royal rank in (parts of) India include Rana, Rao, Raol, Rawal and Rawat. The female form, 'queen', mainly used for a Raja's wife, is Rani (sometimes spelled Ranee), from Sanskrit rĝjñī (compare Old Irish rígain) or Thai Rajanee (Queen).
Raja, the lower title Thakore and many variations, compounds and derivations including either of these were used in and around India by most Hindu and Muslim and some Buddhist and Sikh rulers, while Muslims also used Nawab or Sultan, and still is commonly used in India.
However in Pakistan, Raja is still used by many Muslim Rajput clans as a hereditary title.
Raja is also used as a name by Hindus and Sikhs.
- See Wikipedia article on Raja for more information