Supplementary 和 additional
Supplementary 更具体正式,多半用于 比较专业的 东西
Example,
Supplementary document
University supplementary essay
Additional 用的更全面,非正式正式都可以用
Example,
I want addinitial ketchep for my burger
I need additional papers for my exam
supplementary 与 additional 在用法上有什么区别