They both are much alike in character. (alike是形容词) Great minds think alike. (alike 也是adverb副词) Unlike the others, I never thought of cheating in the exam. He is unlikely to do that on his own. He is likely to trust the words of the liar.
不像一个球: Doesn't look like a ball! unlike a ball 也行,不常用吧
unlikely impossible vs possible likely impossible 是指完全,绝对不可能,unlikely 比较弱的程度吧,没什么可能,但却有可能! possible 和 likely 的话,意思大概相同吧,用法却有些出入 He is likely to finish it on time. 这里我们不能用possible It's possible that he will finish it on time. 这里不能用likely