How do you know if you love someone

Well, it depends.

It usually varies from person to person. This is why love has many different meaning due to the variation from person to person. The experience per se varies so there is no sure way to know if you love someone. The thing is, you will just know if you love someone. Though I said that it varies, there are some similarities in experiences and usually they are. That is for you to decide whether you want to recognize the feeling or not. You can choose to love and you also can decide not to. Yet, you can't choose to love and you can't stop that feeling. It's very complicated my friend. Love isn't something to be understood. It is something to be felt.