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"
W: (adj) accessory [Related to: accessory] (furnishing added support) "an ancillary pump"; "an adjuvant discipline to forms of mysticism"; "The mind and emotions are auxiliary to each other"
W: (adj) accessorial [Related to: accessory] (nonessential but helpful) "accessorial services included sorting and packing"
W: (adj) appurtenant [Related to: appurtenance] (furnishing added support) "an ancillary pump"; "an adjuvant discipline to forms of mysticism"; "The mind and emotions are auxiliary to each other"