In the psychological literature, a distinction is often made between two types of love.[1][2]Elaine Hatfield & G. William Walster define them as:[1]
passionate love, "a state of intense longing for union with another. Reciprocated love (union with the other) is associated with fulfillment and ecstasy; unrequited love (separation) is associated with emptiness, anxiety, or despair."[1][3]
companionate love, "the affection we feel for those with whom our lives are deeply entwined."[1][4]
Companionate love is commonly called "attachment"[8][11][7] (sometimes in relation to attachment theory,[12] but not all authors agree)[5] or compared to strong liking,[5] friendship love[5] or Storge.[5]
Passionate love feelings are most commonly measured with a psychometric instrument (a questionnaire) called the Passionate Love Scale (PLS); however, a study by Sandra Langeslag and colleagues found that the PLS has some questions which actually measure companionate love.[9] This led the team to develop the Infatuation and Attachment Scales (IAS), measuring what they call:[9]
infatuation (similar to passionate love), "the overwhelming, amorous feeling for one individual that is typically most intense during the early stage of love (i.e., when individuals are not (yet) in a relationship with their beloved or are in a new relationship)."[11]
attachment (similar to companionate love), "the comforting feeling of emotional bonding with another individual that takes some time to develop, often in the context of a romantic relationship."[11]
The IAS is designed for more refined measurements than the PLS,[9] but infatuation and attachment can otherwise be considered synonymous as a concept with passionate and companionate love.[9][11]
Evolutionary theories of passionate and companionate love suggest these two types of love exist for different purposes and thus follow different mechanics.[6][7] Passionate love is said to usually only be present in the early stage of a relationship[8] with companionate love often following after;[2][10] however, in a phenomenon called long-term romantic love, intense attraction can remain much longer than is typical for passionate love, but without obsessional elements.[13][14]
Both passionate and companionate love contribute to relationship satisfaction.[5][13] Passionate love is associated more with satisfaction in the early stage of a relationship.[13] Companionate love is associated with satisfaction in the long-term more than the short-term.[13]
Passionate and companionate love can also be further distinguished from a third important type of love, compassionate love, which is love focused on caring about others.[5]