In Terminator 3: Rise of the Machines, the female Terminator sent to kill John Connor is designated T-X.
The T-X is portrayed by Kristanna Loken and serves Skynet as an advanced extermination machine. She combines an endoskeleton with a liquid-metal exterior, allowing her to imitate people and form weapons from her body.
The T-X is sometimes informally called the Terminatrix, but that is a descriptive nickname rather than the film’s formal model designation. She is also distinct from the T-1000 in Terminator 2: Judgment Day, whose body is made entirely of mimetic metal.
The film presents the T-X as a newer generation than the T-800. It can control other machines, including vehicles and robots, which gives it abilities beyond physical disguise and conventional combat.