The Second Great and Bountiful Human Empire was a political entity with influence in three galaxies.
By the 42nd century, it had spread from an overcrowded Earth throughout the galaxy known as Mutter's Spiral and two others, including the Andromeda Galaxy. These three galaxies were collectively referred to as the Tri-Galactic. The currency of the Empire was the credit. The Empire commonly used Ood as slaves until the revolution on the Ood Sphere in 4126 resulted in the slave trade being abolished. (TV: Planet of the Ood)
It was at least partly concurrent with the Earth Alliance, which was the dominant political entity on the Earth itself in 4162, when the Daleks invaded Mutter's Spiral. (AUDIO: Invasion of the Daleks)