"弟弟" 的英语翻译是 "younger brother".
该词源自古英语 "dēorpng"，意思是“小兄弟”或“年轻兄弟”。
例句:
"My younger brother is still in college." (我的弟弟还在上大学。)
"I always look up to my younger brother as a role model." (我总是把我的弟弟当作榜样。)
"My younger brother and I used to fight a lot when we were kids." (我和我的弟弟小时候经常打架。)