This is a word that comes from Latin, and it means ‘day’. The word is used in English in certain fixed expressions like ‘carpe diem’ and ‘per diem’.
Of the two, ‘per diem’ is much more common in India, especially in Government circles. It means ‘per day’; when employees of the government are sent on official duty to other places, they are paid a daily allowance. This is called per diem, and it is given to an individual to meet his daily expenses. Carpe diem means ‘seize the day’