Warp Core

A matter/antimatter reaction assembly (often known simply as an M/ARA) was a type of energy reactor which was fueled by injectors of matter and antimatter into a central reaction element, creating large amounts of energy when those two materials mutually annihilated each other. Matter and antimatter were injected into the M/ARA in an intermix ratio. The dilithium crystal is used to moderate this reaction. These types of power plants were commonly used as warp cores. (TNG: "Coming of Age")