Careful users of the language lament the fact that not many people maintain a distinction between these two words. If you are in the habit changing jobs every two months, you will have several ‘former bosses’, but only one ‘ex-boss’. What is the difference between the two?
Some scholars argue that the word ‘ex’ should be used with the ‘immediate past incumbent’. Your previous boss is your ex-boss, and the ones you had before him are your former bosses. Vajpayee is the ex-Prime Minister of India. Nehru, V. P. Singh, Indira Gandhi, and Gujral, some of the others who preceded Vajpayee, are all ‘former’ Prime Ministers of India.