even if 即使
Even if he is poor,he looks happy.
即令他穷,他看上去很快乐.
(经常用在句首)
even though即使
I like her even though she can be annoying.
尽管她有时很恼人,但我还是喜欢她.
（经常用在句中）
though虽然
although虽然
（这两个似乎没什么很大的区别.）
仅供参考