All the clans of Pandora believe in a shared consciousness through the life force called Eywa, who protects their delicate ecosystem through mutual communication. Avatar: The Way of Water may explain that to give the Na'vi a fighting chance against the humans, Eywa taught English to all the Na'vi clans.
Mo'at and Grace then begin a journey to visit the Tawkami Clan, Pandora's master botanists, hoping that they will have more knowledge of the sickness. At Grace's school, Neytiri and Sylwanin learn to speak English, being regarded as the “top students”, but the school is attacked and Sylwanin is shot and killed.
Na'vi can be learned like any other language, fictional or natural, and the community constantly produces new content and resources to aid in the learning process.
The Naʼvi language has its origins in James Cameron's early work on Avatar. In 2005, while the film was still in scriptment form, Cameron felt it needed a complete, consistent language for the alien characters to speak.
Dr. Paul Frommer, a professor with a PhD in linguistics from the University of Southern California, created the Na'vi language in 2005 for the first Avatar. He based it in part on Polynesian languages, and a dozen or so words crafted by Cameron.
Many of the Na'vi learned to speak English from Grace Augustine's school. Among these former students are: Neytiri, Mo'at, Tan Jala and Tsu'tey. The RDA employs several xenolinguists on Pandora. When humanity first arrived on the moon, it was necessary to establish diplomatic relations with the Na'vi.
Na'vi are monogamous creatures and the process of their reproduction is similar to Terran mammals, as they do possess genitalia; however, though they nurse their young and possess belly buttons where they were once connected to an umbilical cord, the Na'vi are non-placental, thus the details of their internal biology ...
A brand new learner can reasonably expect to be able to hold a conversation in Na'vi in anywhere between 2 weeks to 3 months, so long as they take time to study and practice what they've learned several times a week. Obviously if you don't practice, you won't magically be able to speak it in two weeks.
For one, even if Neytiri is 18 in human years, she's the Na'vi equivalent of a human in their early-to-mid-twenties. This is proven in three different ways: James Cameron has stated that Jake's avatar body is around 17 human years old.
In Cameron's script she's introduced with the descriptor "in human age she would be 18," but that raises as many questions as it answers. As with the math that leads to Jake being 28, Neytiri's birth in the Earth calendar year 2136 and the film's setting in 2154 add up to make her 18, but that's by Earth standards.
Unless that theory is true, Grace was impregnated by someone. Kiri's brothers joke that the scientist Norm could be her father. The movie does not reveal much information about the birth of Kiri. It is unclear whether Kiri was conceived before Grace died and her avatar carried her to term.
Augustine's colleague Norm Spellman (Joel David Moore) was the father and Grace conceived Kiri before the end of Avatar before somehow giving birth in her Avatar body. However, the more interesting theory is that Kiri is literally the child of Eywa due to some sort of immaculate conception.
Her father is not a father, her father is another mother, Eywa, the Great Mother, the sentient life force of Pandora itself that exists in all things there, but is rarely understood. So essentially yes, Kiri was born from Eywa just like Anakin Skywalker was allegedly conceived by the Force itself and its midichlorians.
Na'vi was designed to emulate the general aural feel and flavor of Polynesian languages, such as Maori, one of the three official languages of New Zealand.
For commercial purposes, however—and also for ease of reading by the actors—the “official” transcription is preferred. The letters b, d, j, and q never appear in Na'vi.
Kiri is the inquisitive and intelligent adopted daughter of Jake Sully and Neytiri. Not long after Grace Augustine's death, her dormant avatar was discovered to be pregnant, and Jake and Neytiri adopted the child when she was born. Kiri has an unusually strong connection with Eywa—more than even that of a tsahìk.
It was only when Lo'ak insisted that Neteyam agreed to the rescue. Neteyam risked his life and perished in order to save Lo'ak and Spider from Quaritch. As Jake himself said: "A son for a son". Spider wept for Neteyam as he died as well.
Lo'ak and Kiri are 14 years old in Avatar: The Way of Water, while Tuk is only eight. So, it sounds as if the fourth movie will open with Lo'ak, Tuk, and Kiri at the same ages they are in the third installment, and then they will age six years following the time jump.
