допълнителен означава в английски

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

additional▼(Supplemental or added to)
adjective
[UK: ə.ˈdɪʃ.n̩əl] [US: ə.ˈdɪʃ.n̩əl]

auxiliary▼(supplementary or subsidiary)
adjective
[UK: ɔːɡ.ˈzɪ.liə.ri] [US: agˈzɪ.ljə.ri]

complementary▼(acting as a complement)
adjective
[UK: ˌkɒm.plɪ.ˈmen.tri] [US: ˌkɑːm.plə.ˈmen.tri]

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

plus▼(positive, involving advantage)
adjective
[UK: plʌs] [US: ˈpləs]

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

perquisite [perquisites]▼(benefit beyond salary)
noun
[UK: ˈpɜː.kwɪ.zɪt] [US: ˈpɝː.kwə.zət]

supplement [supplements]▼(supplementary angle in geometry)
noun
[UK: ˈsʌ.plɪ.ment] [US: ˈsʌ.plə.mənt]