Formal:
* நான் உன்னை நேசிக்கிறேன் (Naan unnai nesikkiraen) - This is the most literal and formal way to say "I love you."
Informal:
* உன்னை நேசிக்கிறேன் (Unnai nesikkiraen) - This is a more casual way to say "I love you," often used with someone you are close to.
* நான் உன்னை ரொம்பப் பிடிக்கும் (Naan unnai romba pidikkum) - This translates to "I like you a lot," and is a more playful and affectionate way to express love.
* நான் உன்னை மிகவும் காதலிக்கிறேன் (Naan unnai migavum kadhalikkiraen) - This translates to "I love you very much," and is a more intense way to express love.
Other:
* நான் உன்னைப் பாத்து ரொம்ப சந்தோஷப்படுறேன் (Naan unnai paathu romba santhoshapadureen) - This translates to "I am very happy to see you," and can be a way to express love in a more indirect way.
The best way to say "I love you" in Tamil will depend on the context and your relationship with the person you are speaking to.