loveI have a great love and respect for her.
adorationShe described her complete adoration of her brother.
romanceTheir relationship was nothing but romance and bliss.
passionThe passion had gone out of their relationship.
crushinformalHe had a crush on his French tutor.
head over heels (in love)He fell head over heels in love with his best friend's sister.
puppy loveIt won't last, it's just puppy love.