person, water, paper係情況下會有s?

好難一概而論架

有時強調不同種類個體時可加s
e.g. Different types of fishes

有時加s變左另一樣o野
papers = 證明文件,報紙
e.g. dangerous waters 危險的湖/海
e.g. May I see your papers? 我可否看看你的證明文件?
e.g. I saw that news article in the papers. 我在報紙裏看到那篇報導

有時個字可以用作動詞, 所以第三者用時會加s
soil = make it dirty, water = give water to (plants), wind (讀作wine-d) = 上鏈, etc
e.g. Mary waters her plants everyday. 瑪莉每天都為她的植物灑水

There are just so many "exceptions" in English.
Hope that helps!

當有兩個或以上時，person可轉做people或加s.
Paper就只可加s.
以water,因為他是一個uncountable的字，所以不可加s.