likelihood = probability 都是概率的意思
这两个词是客观的可能性,可以表示有可能,也可以表示没可能,比如：
The likelihood of getting the disease is very high.
The probability of getting 100 points is very low.
possibility 是有可能的意思
there is a possibility that something will happen.
注意,如果把上面的句子改成：
there is a probability that something will happen.
意思就由原来的某事可能发生,变成某事很可能发生.
也就是说probability有两种用法,一个和likelihood一样,表示概率；一个比possbility意思相似但程度更深,表示很可能