Longman Dictionary of Contemporary English - supplement

~1 n 1 something that you add to something else to improve it or make it complete  (a dietary supplement) 2 an additional part at the end of a book, or a separate part of a newspaper, magazine etc  (the Sunday supplements) 3 an amount of money that is added to the price of a service, hotel room etc  (There is a -5 supplement for extra sheets and towels.) ~2 v T always + adv/prep to add something, especially to what you earn or eat, in order to increase it to an acceptable level  (supplement sth by/with)  (Kia supplements her regular salary by tutoring in the evenings.) - supplementation n