Ancient language

Ancient is the name given to the language spoken and written by the Alterans and their descendants, the Ancients and the Ori. The language is fairly similar to Latin spoken on Earth.

Speakers
Several people at Stargate Command were successful in understanding written and spoken Ancient. Daniel Jackson was the one who unlocked the mysteries in that language, so that more could learn it. Other people who are fluent in the language or at least understand it are Jonas Quinn, Rodney McKay, Elizabeth Weir, and an unnamed Air Force Linguist.

Also, at two occasions, Jack O'Neill was able to speak it, after getting huge amounts of information from the Ancients' Repository of Knowledge, but the Asgard were forced to erase it from his memory, and he never retained any knowledge.

Daniel Jackson further expanded his knowledge of the Ancient language when he ascended.

To protect his computer systems, Anubis used elaborate ciphers coded in the oldest known Ancient dialect. Despite the Goa'uld's long known history of acquiring Ancient relics, the Tok'ra were unable to translate them.

Some of the Athosians have displayed knowledge of Ancient, and some give prayers in Ancient

The Wraith language is derived from Ancient.

Words upside down can have different meanings.