Oh, this is about English — some examples would have been nice to have. “Tent” and “tant” are always pronounced the same in French, and like “ce” and “se”, are complete words in that language.
In English: Sometimes the S is pronounced /z/, whereas the C is never pronounced /z/. Sometimes the noun will end in -ce while the verb will end in -se — but you never know. As unstressed endings, -tent and -tant are pronounced identically — the vowel is reduced to a schwa in both cases. That’s why so many native English speakers misspell words so much — proper spelling is often a sign of autocorrect (or of a non-native speaker, lol). To some extent, -tant versus -tent depends on the Latin root of the word, but if you don’t know Latin, that’s no help, and a lot of the time English has changed the spelling for no apparent reason.
Let me know if you’ve benefited (or not) from my attempts to answer your question.