Using 也 (ye3) vs. 又 (you4)?
也 means "too", "also": 我也是. Me too.  

又 means "again": 今天又下雨了. It rained again today. 

In informal speech, 也 is more neutral. It simply conveys the information that something is the same as something else. 他也是一个学生。He is also a student.

又 can have a negative connotation. 他又这样! He is doing it again!