Here's why:

* Hydrogen bond donor: The -OH group in an alcohol can act as a hydrogen bond donor. The hydrogen atom in the -OH group is partially positive, allowing it to form a hydrogen bond with an electron pair on a neighboring molecule.

* Hydrogen bond acceptor: The oxygen atom in the -OH group is partially negative, making it a hydrogen bond acceptor. It can form a hydrogen bond with a hydrogen atom from another molecule (like another alcohol or water).

Therefore, a single alcohol molecule can participate in two hydrogen bonds: one as a donor and one as an acceptor.