yeah比yea多了一个字母y,哈哈
yea：n.肯定,赞成
yeah：adv.( yes的俗音)；（用于表示对后说的话不相信）；（用于作出回应）哦；是
可见两个词词性都不一样.yeah是应答短语,可以单独成句；而yea是名词,不能单独成句.
yea英文解释：
Yea is an old-fashioned,poetic,or religious word for 'yes'.
Yea is sometimes used to mean 'yes' when people are talking about voting for or agreeing to do something.