Radha...Her Love was unconditional and supreme

When do you know when you are in love? or love anyone...the fact is that no two individuals can profess to love each other in exactly the same way and same depth...
Some suggestions:
You are in love when you would rather not live without the other person.
When he or she is the first that springs to mind in happiness and grief
When the other person is a constant companion even in absentia
When sometimes your loved one's happiness takes precedence over yours

Such a loving may or may not last a lifetime, but whatever the span it soaks up your entire being...
Excerpts from 'Are you really in love' Times Life Sept, 27th 2009 by Vinita Dawra Nangia

However I believe that there are various kinds of Love
1) You scratch my back and I shall scratch yours...
2) Romeo Juliet, Heer Ranjha, Sasui Punoo kind of love...where it is believed that they were soul mates or One soul divided in two or twin souls...
...and then we have the Spiritual Love...totally unconditional...We have never seen God...yet a lot of us Love Him...Radha's love for Krishna absolutely unconditional...Meera who sings...Jahaan bithaave ut hi baithoon jo de soyee khaaoon, Meera ke Prabhu Giridhar Naagar, Baar baar bali jaaoon...