The language of the Klingons, called tlhIngan Hol by its speakers, a harsh and compact tongue developed for the films by the linguist Marc Okrand.
Klingon, or tlhIngan Hol, is the principal language of the Klingon Empire. It is guttural and direct, and it is rich in terms for combat and honour. Its best-known word is Qapla', meaning success, which serves as a farewell.
The first few words were devised by James Doohan for Star Trek: The Motion Picture. The linguist Marc Okrand built these into a working language with its own grammar for Star Trek III: The Search for Spock and published The Klingon Dictionary in 1985. He continued to supply dialogue for later films and series.
On screen the language is heard most in the films, in The Next Generation and Deep Space Nine episodes about Worf, and in the first season of Discovery, where long scenes among Klingons are played entirely in it with subtitles.