“进贡国”常见的英文表达是 tributary state 或 tributary nation,也可表述为 a state/nation that pays tribute 。
“tributary” 本身有“进贡的;附属的”含义,“tributary state” 就是指历史上向更强大的政权或国家定期进贡以换取和平、保护或某种认可的附属国。例如:In ancient times, many small kingdoms became tributary states to the powerful empire.(在古代,许多小王国成为强大帝国的进贡国 。 )