The language has struggled to keep a healthy speaker base, although this problem has been alleviated to some extent by extensive education programs in the Navajo Nation.

In World War II, speakers of the Navajo language joined the military and developed a code for sending secret messages.

Most Navajo vocabulary is Athabaskan in origin, as the language has been conservative with loanwords due to its highly complex noun morphology.

It was borrowed into Spanish to refer to an area of present-day northwestern New Mexico, and later into English for the Navajo tribe and their language.

[14] The Apachean languages, of which Navajo is one, are thought to have arrived in the American Southwest from the north by 1500, probably passing through Alberta and Wyoming.

[15][16] Archaeological finds considered to be proto-Navajo have been located in the far northern New Mexico around the La Plata, Animas and Pine rivers, dating to around 1500.

When the United States annexed these territories in 1848 following the Mexican–American War,[23] the English-speaking settlers allowed[citation needed] Navajo children to attend their schools.

In efforts to acculturate the children, school authorities insisted that they learn to speak English and practice Christianity.

[25] Robert W. Young and William Morgan, who both worked for the Navajo Agency of the Bureau of Indian Affairs, developed and published a practical orthography in 1937.

The language was considered ideal because of its grammar, which differs strongly from that of German and Japanese, and because no published Navajo dictionaries existed at the time.

Native American language use began to decline more quickly in this decade as paved roads were built and English-language radio was broadcast to tribal areas.

[29] Adding to the language's decline, federal acts passed in the 1950s to increase educational opportunities for Navajo children had resulted in pervasive use of English in their schools.

[29] This effort was aided by the fact that, largely due to the work of Young and Morgan, Navajo is one of the best-documented Native American languages.

In 1980 they published a monumental expansion of their work on the language, organized by word (first initial of vowel or consonant) in the pattern of English dictionaries, as requested by Navajo students.

[27] The Native American language education movement has been met with adversity, such as by English-only campaigns in some areas in the late 1990s.

Statistical evidence shows that Navajo-immersion students generally do better on standardized tests than their counterparts educated only in English.

Some educators have remarked that students who know their native languages feel a sense of pride and identity validation.

[36] This program includes language, literature, culture, medical terminology, and teaching courses and produces the highest number of Navajo teachers of any institution in the United States.

[47][48] On October 5, 2018, an early beta of a Navajo course was released on Duolingo, a popular language learning app.

However, some linguists have suggested that Navajo does not possess true tones, but only a pitch accent system similar to that of Japanese.

[66] Other linguists such as Eloise Jelinek consider Navajo to be a discourse configurational language, in which word order is not fixed by syntactic rules, but determined by pragmatic factors in the communicative context.

[69] Furthermore, Navajo negates clauses by surrounding the verb with the circumclitic doo= ... =da (e.g. mósí doo nitsaa da 'the cat is not big').

[77] Most nouns are not inflected for number,[76] and plurality is usually encoded directly in the verb through the use of various prefixes or aspects, though this is by no means mandatory.

Other prefixes that can be added to nouns include possessive markers (e.g., chidí 'car' – shichidí 'my car') and a few adjectival enclitics.

The Athabaskan family is fairly diverse in both phonology and morphology due to its languages' prolonged relative isolation.

For example, the phrase for English tank is chidí naaʼnaʼí beeʼeldǫǫhtsoh bikááʼ dah naaznilígíí 'vehicle that crawls around, by means of which big explosions are made, and that one sits on at an elevation'.

An apostrophe (ʼ) is used to mark ejective consonants (e.g. chʼ, tłʼ)[87] as well as mid-word or final glottal stops.

[54] The voiceless glottal fricative (/h/) is normally written as h, but appears as x after the consonant s (optionally after sh) at syllable boundary (ex: yiyiis-xı̨́), and when it represents the depreciative augment found after stem initial (ex: tsxı̨́įł-go, yi-chxa).

[92] Navajo original: Ashiiké tʼóó diigis léiʼ tółikaní łaʼ ádiilnííł dóó nihaa nahidoonih níigo yee hodeezʼą́ jiní.

Áádóó baa nahidoonih biniiyé kintahgóó dah yidiiłjid jiníʼ  (...) English translation: Some crazy boys decided to make some wine to sell, so they each planted grapevines and, working hard on them, they raised them to maturity.