Cait is a planet in the Lynx constellation, the homeworld of Lt. M'Ress. There is only one other planet in the system, and it is uninhabited. The atmosphere, mass and gravity of Cait are all near Earth normal.

The felinoid Caitians and the warlike Kzinti share common roots in the deep past — as do Vulcans and Romulans. As with the Vulcans and the Romulans, the two groups went their separate ways to develop as two entirely different civilizations. The Caitians are fierce warriors when so called upon, but pride themselves on their accomplishments in arts and philosophy rather than on the martial arts.

Natives of Cait tend to be small and sinewy; the females are as delicately dainty as the Siamese or Abyssinian cats of old Earth. Their family units are extremely close.