There is very little known about the Cardassian language, other than its proper nouns (see Cardassians and Cardassia for names of people and places respectively).

Writing system

Cardassian writing is composed of slender rectangular letters usually widening at the top. Lines of text are written both horizontally and vertically, radiating out from an elaborate circle motif. Lines of text also incorporate dots. (TNG: "Chain of Command, Part II"; DS9: "Tribunal", "Things Past")

Keiko O'Brien's classroom aboard Deep Space 9 featured a chart with the Human, Ferengi, Bajoran, and Cardassian alphabet. (DS9: "The Nagus", "In the Hands of the Prophets")

Military and government

"Gul" is a rank that seems roughly analogous to the Federation rank of captain; "glinn" is a rank below Gul. "Legate" is a rank above gul (see Cardassian ranks). (TNG: "The Wounded")

The Detapa Council is the highest civilian government body, although we are never given a clue as to what the word "Detapa" means. However it could mean civilian or be the name of the location the Council was first constituted. (DS9: "The Way of the Warrior")

Miscellaneous

"Odo'ital" is Cardassian for "nothing". Odo was called odo'ital when he was studied at the Bajoran Institute of Science. (DS9: "Heart of Stone")

"Yamok" sauce is a common Cardassian condiment. Yamok may refer either to what the sauce is made from, or the actual sauce itself. (DS9: "Progress")

"Nor" seems to carry connotations of either "station" or "base"; Terok Nor and Empok Nor have this word in their names in the same position. (DS9: "Cardassians", "Empok Nor")