Chinese-all-day-breakfast/MD/All-Day-Breakfast/docs/g1-21.md

Word usage: 也 and 還

也 is used to mean "the same" as the previous statement. Hence the relationship between the statement introduced by 也 and the previous one is a /parallel/ relationship. 還, on the other hand, introduces an /additional/ element to the previous statement.

e.g. 你有一個問題﹐我也有一個問題。
    You have a question; I also have a question. The two are
    parallel here.
我還有一個問題。
    I have already had some questions, but I still have one more.
    This is /in addition to/ the previous ones.

Under certain circumstances, 也 and 還 are interchangeable, but with different emphasis:

王老師教我們漢字和語法﹐他還教我們口語。
王老師教我們漢字和語法﹐他也教我們口語。

Although both sentences can be roughly translated as "Professor Wang teaches us Chinese characters and grammar; he also teaches us conversation", their emphasis is different: the first sentence stresses the fact that Wang teaches conversation /in addition to/ the other subjects he teaches, whereas the second simply enumerates the three subjects he teaches without prioritization.