1. Compensation arising from office or employment.
2. (archaic) Advantage.
An emolument can include standard compensation (fees, wages) as well as perquisites (tips, perks, privileges of position, expected benefits).
Etymology: from Middle French émolument, from Latin emolumentum, advantage or gain. Possibly originally from emolere, grind out, as in payment to a miller for grinding corn.
Article I, section 6 of the U.S. Constitution says "No Senator or Representative shall, during the Time for which he was elected, be appointed to any civil Office under the Authority of the United States, which shall have been created, or the Emoluments whereof shall have been encreased during such time...." So, for example, if a new political position is created that pays more than a senator's current salary, the senator can't resign in order to take the position.
The word is still in use today, most often in legal or financial discussions, to refer to all forms of compensation rather than just a salary.