"I love you" is the common terminology used to express the love between two lovers. Love is used in wide term in English. A person expresses his love to his lover by saying "I love you", the same sentence is used to express the love for mother and father or anybody else. "Kadhal" in Tamil is used in very narrow way to express the feelings between two people, who think they love each other, but I don't think, love and kadhal mean the same thing. English doesn't have any equivalent to "Kadhal" in Tamil. It is something like, how they do not have any separate words for "Periyappa, Chithappa, Chithi, Athai and Mama, the same way they do not have separate word for "Kadhal" in English. No one says "Naan unnai Kadhalikaren" towards his mother, whereas in English, "I love you" can be used to express the love between two lovers as well as towards parents. So, it obviously shows that they do not have the exclusive word "kadhal" in their language. I don't know, who equaled the English love with Tamil kadhal. They are two different words, mean two different feelings. Tamil Kadhal is used by peopel who have special feelings towards something, that special feeling is more than love, it often involves physical attraction too. kadhal is mixture of more than love and lust. "Love" is pure love, it may involve physical attraction or not. So, Tamil kadhal is very different than the wide term of Love in English.