Formal:
* நீ இன்று அழகாக இருந்தாய் (nee inru azhagaga irunthai): This is the most literal translation and is a polite way to express appreciation.
* நீ இன்று மிகவும் அழகாக இருந்தாய் (nee inru migavum azhagaga irunthai): This emphasizes the beauty and is more appropriate for a closer relationship.
Informal:
* நீ இன்னைக்கு ரொம்ப அழகா இருந்த (nee innaikku romba azhaga iruntha): This is a casual and friendly way to say it.
* நீ இன்னைக்கு அழகா இருந்தே (nee innaikku azhaga irunthae): This is even more informal and could be used with close friends or family.
You can also add a compliment about a specific feature:
* நீ இன்று உன் கண்கள் அழகாக இருந்தது (nee inru un kannkal azhagaga irunthathu): "Your eyes were beautiful today."
* நீ இன்று உன் புடவை அழகாக இருந்தது (nee inru un pudavai azhagaga irunthathu): "Your saree looked beautiful today."
Remember to adjust the language based on your relationship with the person you're speaking to.