Formal:
* இருக்கக் கூடாது (irukka koodaadu): This is the most direct and formal translation, meaning "should not be" or "must not be."
* இருந்திருக்கக் கூடாது (irundhirukka koodaadu): This emphasizes that something shouldn't have been in the past.
* இருக்க வேண்டாம் (irukka vendaam): This is a polite and less forceful way of saying "should not be."
Informal:
* வேண்டாம் (vendaam): This is the most common and informal way to say "should not be" or "don't be."
* இருந்தா கூடாது (irundaa koodaadu): This is a more emphatic way of saying "it shouldn't be" or "it's not acceptable."
Example:
"You shouldn't be late."
* நீங்க தாமதமா இருக்கக் கூடாது. (Neega thamadhama irukka koodaadu.) (Formal)
* தாமதமா இருக்க வேண்டாம். (Thamadhama irukka vendaam.) (Informal)
Ultimately, the best translation depends on the specific situation and the desired level of formality.