Rasarnavasudhakara 2.240

2.240

tatra ratiḥ-
yūnor anyonya-viṣayā sthāyinīcchā ratir bhavet |
nisargeṇābhiyogena saṃsargeṇābhimānataḥ ||

Among them, love: / Durable desire directed toward each other in a youthful couple is love. / It arises by nature, by devotion, by association, and by attachment;