鸡同鸭讲：字面意思为鸡和鸭讲话，语言不通，一般用来形容两人所用非共同语言，无法沟通的意思。注：对于初次见面不熟悉的朋友这个词还是不要随便用，因为会显得没有礼貌。如果是很熟的朋友，开玩笑什么的都没有关系的话，那么就可以用。因为这个词属于中性词来的。 一目了然：一眼就看得很清楚。 像图书馆由于使用了图书分类，要找什么类别的书可以说一目了然。（注：一目了然偏重在表示了解得十分容易，不表示一看就懂的意思。）

Chicken can't understand what ducks say, so 鸡同鸭讲 just means that someone has chosen the wrong audience or someone waste good acts on others who won't understand. eg, 一目了然 just by taking a glance and then you get it. Tom: 你知道中国是区域自治吗？ (You know that China has instituted a system of regional autonomy in minority areas.) Anna: 真的假的？我一直以为中国是联邦制，跟美国一样... （what？ I was always thinking China got a federal system, just like the United States） Tom: 哎，算了，我在这简直是鸡同鸭讲，中国怎么可能是联邦制啊...你不会连这都不懂吧？ （Never mind, when it comes to politik and law, we couldn't communicate xDxD. How could China even be federalism, so you really don't know that do you?） Anna：你才是鸭子呢！中国虽然不是联邦制，不过也快了...(Oh, come on, you are the person who can' figure out the trend, china is still not ferdalism, but it will be soon...) Tom: 这种趋势怎么可能一目了然， 你不会做白日梦梦见的吧,你不知道联邦制都是独立选举吗？... (How can I just by taking at a glance get to this conclusion that China will one day be ferdalism, so you must be daydreaming...Don't you see that all the staates who has ferdalism has it's seperated election system?)

鸡同鸭讲 是广东话，意思是语言不通，形容两个人操非共同语言，无法沟通。 一目了然 “目” 在古汉语中是“眼睛”的意思，“了”是“了解”的意思，“然”是“.......的样子” 的意思 所以这个成语的意思是 “一眼就看的很明白很清楚”

1. 鸡同鸭讲：没有共同语言，类似的还有牛头不对马嘴！！！when you talk with someone, but he can not understand what you said or what he said is no related with your topic,you can say:真实鸡同鸭讲。 2.一目了然：当别人让你看人或者事物的时候，一眼就看的很清楚，或者一看就知道是怎么回事！

鸡同鸭讲:generally used in this conditon,there is no common language between two people, so they can unable to communicate.That is to say,someone cannot understand completely what u talked. 一目了然:people understand a thing very easily,just ,just take at a glance.