In
host-guest chemistry, an
inclusion compound is a
complex in which one
chemical compound (the "host") forms a cavity in which molecules of a second "guest" compound are located. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which guest molecules can fit. If the spaces in the host lattice are enclosed on all sides so that the guest species is ‘trapped’ as in a cage, the compound is known as a
clathrate. In
molecular encapsulation, a guest molecule is actually trapped inside another molecule.