[文法] may的用法

[lifeisdrama (人生如戲)]

想請問各位板友

下列這些句子中的may

(1)Write to him at once so that he may know in time.
                                   ~~~

(2)Speak clearly so that they may understand you.
                              ~~~

感覺上這些may好像不加也可以??

請問這是什麼用法?

謝謝你的回應

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→ versavice:加強(調整)語氣
→ lifeisdrama:所以也可以不加嗎?
推 blueautumn:may有"才能夠"的意思  加了語意才比較通順
→ lifeisdrama:謝謝~