有一條成語“涇渭分明”，
說的是兩條河一濁一清，
就在那甘肅陝西兩省境，
兩條河彙合後清濁分明。
假如是生活中有兩種事物，
兩事物有特點各自不同，
便可將這條成語用，
把它們確切地加以形容。
如人們對事物有愛有恨，
又比如對某事反對或讚成，
切不可人雲亦雲缺乏主見，
有立場有主見才涇渭分明。
River Jing and River Wei
Are Sharply Different
In Chinese there is an idiom called“River Jing and River Wei Are Sharply Different”。It tells of two rivers-one is clear and the other is dusty yellow。The two rivers are respectively in Gansu and Shaanxi。It is interesting because it keeps half clear and half muddy after they merge。
When you meet two things in daily life which bear a distinct difference，you can use the ready-made idiom to definitely describe this case。
Another instance is when you hate one thing while you love another and when you are for something and against something else。
Try not to echo what others say and keep a dull-witted head hold an opinion and you will be able to tell the difference。