<unk> in supramolecular chemistry refers to a stacked arrangement of aromatic molecules, which interact through aromatic interactions. The most popular example of a stacked system is found for consecutive base pairs in DNA.<unk> also frequently occurs in enzymes where two relatively non-polar rings have overlapping pi orbitals. The exact nature of such interactions (electrostatic or nonelectrostatic) is a matter of debates.
Stacking 
Extraction 
Strangling
Friction
Chemotaxis
Swelling 
Deceleration
Reverting