Female Trill who was the first host to the Dax symbiont. Lela Dax was a legislator, one of the first women to serve as a council member on the Trill homeworld. When she started out, she would speak using lots of emphatic gesturing. She found out that some of her male colleagues were making fun of her for this, so she started to restrain herself by holding her hands behind her back; that became a habit which remained with Dax throughout the symbiont's several lifetimes. Jadzia Dax, the eighth host, learned about this when she invoked the Trill Rite of Closure or "Zhian'tara" during which she transferred the memories of Lela into her friend Kira Nerys.
Lela had a son named Ahjess. When he was young, Lela couldn't sleep through a whole night for weeks, because after Ahjess was tucked into bed at night, he would climb into his mother's bed two hours later for attention. (Jadzia recalled this when talking with Miles O'Brien about his children.)
The exact time of Lela Dax's joined life is unknown, but it was probably in the 21st century.