Cardassia V was the inhabited fifth planet in the Cardassian system, in the Alpha Quadrant. The planet was affiliated with the Cardassian Union.
In 2370, Kono was wanted there for stealing bone-carvings from a museum. (DS9: "Shadowplay")
In 2375, the location of Cardassia was labeled on a tactical map that was displayed in the wardroom of Deep Space 9. (DS9: "When It Rains...", okudagram)
This planet was only mentioned in dialogue.
"car-DASS-ee-uh" was the pronunciation for this planet's name from the script pronunciation guide for "Tribunal". 
According to a stellar cartography map, seen in the Star Trek: Deep Space Nine Technical Manual, the Cardassian system was located in the Bajor sector. 
According to Star Trek: Star Charts (pp. 37, 43, 46), Cardassia V (Cardassia Minor) was classified as a M-class world.