The ambassador was known for his distinguished service to his country.

distinguished 是形容词，来自动词 distinguish（区分、辨别）的过去分词形式。前缀 dis- 表示"分开"，词根 -stingu- 与 sting（刺）同源，表示"刺出标记来区分"。distinguished 形容一个人因其卓越成就而"与众不同、杰出的"。