Nacelles are engine housing structures on starships.
Warp nacelles on starships house warp coils, which are fed by plasma conduits from a vessel's warp core. The coils create a subspace field around the ship that allow the ship to travel at warp velocities. The most common configuration is two nacelles, however a vessel can travel at warp with more than two nacelles or just a single nacelle.
External link[]
- Nacelle article at Memory Alpha, the canon Star Trek wiki.