一般无二 generally without two
Explanation
一般无二的意思是完全一样，没有不同的地方。用来形容两个事物或人完全相同，没有区别。
Generally without two means exactly the same, there is no difference. It is used to describe two things or people that are exactly the same, without any difference.
Origin Story
在遥远的古代，有一个名叫阿宝的少年，他有一个双胞胎哥哥名叫阿虎。阿宝和阿虎长得一模一样，性格也十分相似。他们兄弟俩从小一起玩耍，一起学习，无话不谈。他们的一言一行都一般无二，连老师都经常认错他们。 有一天，阿宝和阿虎去参加村里的比武大会。阿宝擅长大刀，阿虎精通拳法。比赛开始后，阿宝和阿虎都表现出色，他们互相配合，默契十足，最后取得了比赛的胜利。 村里的人们都为阿宝和阿虎感到高兴，他们兄弟俩也因为这次比赛而名声大噪。从此以后，阿宝和阿虎便被人们称为“双胞胎兄弟”。
In ancient times, there was a boy named Abao who had a twin brother named Aohu. Abao and Aohu looked exactly alike and had very similar personalities. The two brothers played together from a young age, studied together, and had no secrets from each other. Their every word and action was the same, even the teachers often mistook them for each other.
Usage
这个成语主要用来形容两个人或事物完全相同，没有区别。一般用于比较两个事物或人，强调其相同之处。
This idiom is mainly used to describe two people or things that are exactly the same, without any difference. It is generally used to compare two things or people, emphasizing their similarities.
Examples
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这两件东西完全一样，一般无二。
zhe liang jian dong xi wan quan yi yang, yi ban wu er.
These two things are exactly the same, there is no difference.
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他们兄弟俩的性格一般无二，都是非常开朗的。
ta men xiong di liang de xing ge yi ban wu er, dou shi fei chang kai lang de.
The two brothers are exactly alike in character, they are both very cheerful.