Chanukah celebrates the return of holiness to the Temple after the contamination of the Greeks. Chanukah took place in Israel during the Hellenistic oppression called golus Yavan. This third exile lasted 180 years, and was dubbed the exile of darkness because the Greeks made every effort to make Jews see and understand the world in a way which was alien to the Torah. Darkness, because nothing is as dark as the enslavement of the human mind. The golus Yavan is always referred to as darkness because it took away the light of Torah.
Darkness is the absence of light.
Things that are negative we call darkness. But you can combat Evil in the world. Chanukah expresses the victory of light over darkness. Look closely at the nature of a flame. It is to rekindle in ourselves the light of the triumph over darkness.