How do you say die in Japanese?

shinu is the verb meaning 'to die'.

shinde kudasai means please die.

shinimasu means i die or i will die

shinimasen means i won't die or i don't die (as in now... that second in time)

shinimashita means i did die

shinimasendeshita means i did not die

(or if referring to someone else, you die or you will die or the meaning just referring to someone or something else)