In 1977 psychologist Dorothy Tennov published research on the experience of being in love. To distinguish it from other kinds of love, she coined a new term, “limerence.”
Full details follow in her 1979 book, Love and Limerence: The Experience of Being in Love. Typical components include
• Intrusive thinking about the person who is the object of limerence.
• Acute longing for reciprocation
• Fantasies of reciprocation
• Obsessive examination of any possible signs of reciprocation
• Extreme emotion (e.g. euphoric joy or despair), depending on reciprocation
• Fear of rejection
• Unsettling shyness in the limerent object’s presence
• Feelings intensified through adversity, obstacles, or distance
• Emotional dependence on the littlest positive reaction from the limerent object
• Heightened awareness and high energy for pursuing the limerence
• Average duration of two or three years
The first time I heard of limerence was from a friend I was definitely in some limerence toward. It struck me as a useful, even delightful concept. He and I danced to the tune of our mutual attraction, for the duration of the evening. Then I saw little of him after that. But I was fortunately not stricken with disappointment so much that time, as I have been with other limerence.
Because it can get bad.
 Roy Reed, “Love and Limerence,” New York Times, Sept. 16, 1977, 51.