Definition: Recognize or find out. [Oxford Dictionary]

语义较笼统，着重精深与准确的观察力，不一定有能分辨关系密切的各项事物的含义。（词组学习: discern from从…上辨别出）

例句：

The man couldn't discern between right and wrong.

那人是非分辨不清。

I can discern no difference between the two policies.

Definition: 1. Make an unjust or prejudicial distinction in the treatment of different categories of people, especially on the grounds of ethnicity, sex, age, or disability. 2. Recognize a distinction; differentiate. [Oxford Dictionary]

语气强，指从十分相似的事物中辨出差异，尤其把好坏区分开来。（这个词语还有歧视的意思，名词形式discrimination，作为辨别时，还有一个词组：discriminate...between...识别，辨别；而作为歧视时，也有一个词组:discriminate against歧视……，有差别地对待。）

例句：

They can discriminate hundreds of colours.

他们能分辨上百种颜色。

A teacher must not discriminate between pupils.

老师对学生应当一视同仁。

Discriminate among the options available.

Definition: 1. Recognize or treat (someone or something) as different. 2. Manage to discern (something barely perceptible). 3. (distinguish oneself) Make oneself worthy of respect by one's behaviour or achievements. [Oxford Dictionary]

普通用词，指辨别者的能力或实际观察到的区别，强调辨别所需的技巧。（词组学习：distinguish between辨别，识别（两者）之间的不同；distinguish from区别，辨别；distinguish one thing from another将一事物于另一事物区别开来；distinguish oneself使扬名；使杰出。）

例句：

Distinguish good from evil

分辨善恶

Distinguish things into classes

把东西分成类

Distinguish between silk and rayon

分清丝和人造丝