добавочный meaning in English

accessory▼(having a supplementary function)
adjective
[UK: ək.ˈse.sə.ri] [US: æk.ˈse.sə.ri]

adventitious▼(from an external source)
adjective
[UK: ˌæd.ven.ˈtɪ.ʃəs] [US: ˌæd.ven.ˈtɪ.ʃəs]

extra▼(beyond what is due, usual)
adjective
[UK: ˈek.strə] [US: ˈek.strə]

supplementary▼(additional)
adjective
[UK: ˌsʌ.plɪ.ˈmen.tri] [US: ˌsʌ.plə.ˈmen.tə.ri]

top-up▼(additional)
adjective