Formal:
* "Você é o meu único amor." (You are my only love.) - This is the most direct and formal translation.
* "Você é a minha única paixão." (You are my only passion.) - This emphasizes the intensity of your feelings.
Informal:
* "Você é meu único amor." (You are my only love.) - This is a more casual version of the formal option.
* "Você é tudo pra mim." (You are everything to me.) - This is a more emotional and poetic way to say it.
* "Você é o meu único e verdadeiro amor." (You are my one and only true love.) - This emphasizes the exclusivity and genuineness of your love.
More specific:
* "Você é a única pessoa que eu quero." (You are the only person I want.) - This emphasizes that the other person is the only one you desire.
* "Você é a única pessoa que me faz feliz." (You are the only person who makes me happy.) - This emphasizes that the other person is the source of your happiness.
Important note:
* Portuguese has two genders: masculine and feminine. You need to use the appropriate gender for the person you are addressing. For example, if you are addressing a man, use "o" (the), "meu" (my), and "você" (you) in the masculine form. If you are addressing a woman, use "a" (the), "minha" (my), and "você" (you) in the feminine form.
* The translation can also be influenced by the level of formality and the specific relationship you have with the person you are speaking to.
Ultimately, the best way to say "are my one and only" in Portuguese depends on the context and your personal style.