S: (n) addition, add-on, improver (a component that is added to something to improve it) "the addition of a bathroom was a major improvement"; "the addition of cinnamon improved the flavor"
S: (n) computer accessory (an accessory for a computer) "when you add in all the computer accessories you are going to need the computer gets pretty expensive"
S: (n) fitting (a small and often standardized accessory to a larger system)
S: (n) fixings, trimmings (the accessories that normally accompany (something or some activity)) "an elaborate formal dinner with all the fixings"; "he bought a Christmas tree and trimmings to decorate it"