Navajo is linguistically related to Apache and some North Pacific Coast languages. It is totally unrelated to Indo-European languages. Sound and sentence structure is very different to English. It has a large and flexible vocabulary.
It's sounds quite different, and it is difficult to learn unless you are a Navajo baby. So difficult in fact, that in WWII Navajo was used as a means of communication in code by the Armed Forces.
Source
Mission to the Navajo by Sterling Betty
Does anyone have examples of the sentence structure?