Final answer:
Companionate love is the form of love that Lou and Rachel have, characterized by commitment and intimacy but lacking passion.
Step-by-step explanation:
The form of love that Lou and Rachel have, characterized by commitment and intimacy but lacking passion, is called companionate love according to Robert Sternberg's triangular theory of love. Companionate love is a type of love that is high in intimacy and commitment but low in passion.