Trill written language
Trill language was the spoken language of the Trill.
When performing the
ceremony, a zhian'tara Guardian says a special ritual over a vat of symbiont mud, to transfer the telepathic presence of a previous host. ( : " DS9 ")
Star Trek: Celebrations (pp. 126-127) refers to this as "the ancient Trill language," and suggests this may be "a relaxation technique, a mantra to allow for the memories to move from one calm body to another calm body." Ezri Dax recited a similar ritual individually to commune with Joran. ( : " DS9 ")
Field of Fire
The Trill written language is composed of rounded-triangles with squiggly lines in them.
Miles O'Brien was able to read payroll records in the Trill written language. ( : " DS9 ", " Equilibrium ")
32nd century, Trill weapons and the towels used in the Caves of Mak'ala featured Trill script. ( : " DIS ")
Forget Me Not
The Trill language used in "Forget Me Not" was devised by linguist Nick Farmer. 
Examples of spoken Trill
I'nora, ja'kala Dax... zhian'shee, Lela tanus rem...Gon'dar, Jadzia-tor...
(The Guardian reaches and places a hand to the small of Dax's back, then to the back of Kira's head...)
Jadzia, zhian'tara vok... Tu
Dax, zhian'tani ress... Zhian'par, Lela garu'koj... Transfer of personality of
Lela Dax from Jadzia Dax. Jadzia, zhian'tara vok... Tu Dax, zhian'tani ress... Zhian'par, Odo garu'koj...
Transfer of personality of Curzon Dax from Jadzia Dax to Odo. ( : " DS9 ") Facets
Ezri contacts Joran
I'nora, ja'kala vok... 'za Ezri... zhian'tara rek... pora'al Zheem Dax... Tanas Rhem Joran.
Ezri Dax attempts a variation of the zhian'tara to commune individually with Joran. ( : " DS9 ") Field of Fire
The scripted word order was: "...Joran Tanas Rhem. "
'za Ezri Tanas Rhem Joran.
Ezri tries further, after initially being unsuccessful.
Joran Tanas Rhem. Vok Ezri... Joran Tanas Rhem.
Ezri continues trying until successful.
Iituja ro motux shi zhian kalasham tanula ranupakala majashsh.
We welcome you home. Leader Pav, Commissioner Vos and Guardian Xi upon witnessing the restoration of the Tal symbiont's memories. ( : " DIS ") Forget Me Not
The English translation was not provided in the episode, but comes from an interview with language creator Nick Farmer. Farmer notes that the line makes use of agglutination, gemination, and second person singular joined-Trill pronouns.  Farmer shared the Trill transliteration on Twitter.