Per diem is a financial term used to describe a payment which is made each day, i.e. an allowance of travel expenses for somebody on a business trip.
Per diem is a Latin term which translates literally to ‘by the day’ or ‘per day.’ It is believed to have come into use as part of the English language around 1809.
Usually, per diem does not apply to the food and travel costs one may be provided with when undertaking voluntary work, i.e. an up-and-coming actor who is not being paid for their time but is having their basic expenses covered is traditionally not an example of per diem.
Per diem is generally a fixed amount of money provided to cover expenses that an employee or similar might incur on a trip or similar. It is worked out when taking into consideration costs of travel, lodging, food etc. It is worked out in advance and the employee is not required to return any leftover money they do not spend, as it has already been budgeted for.