It is most closely related to Tongan and slightly more distantly to other Polynesian languages such as Māori, Samoan, and Hawaiian.

Examples of differences in vocabulary are volu (Tafiti) vs matā (Motu) for scrape, scraper and lala (Tafiti) vs kautoga (Motu) for guava (plant); examples of differences in form include hafule (T) / afule (M), aloka/haloka, nai/nei, ikiiki/likiliki, and malona/maona.

Hiatus is the separate pronunciation of two adjacent vowels, as opposed to diphthongs, which are written as two letters but pronounced as one sound.

Consonant clusters in borrowed words are broken up with epenthetic vowels, e.g. English 'tractor' becomes tuleketā.

The Niuean language does not contain the glottal stop, which is present in its closest relative, Tongan.

Niuean orthography is largely phonemic; that is, one letter stands for one sound and vice versa[clarification needed].

The traditional alphabet order, given with the traditional names of the letters, is ā, ē, ī, ō, ū, fā, gā, hā, kā, lā, mō, nū, pī, tī, vī, rō, sā.

Sperlich (1997) uses an alphabetical order based on English for his dictionary: a, ā, e, ē, f, g, h, i, ī, k, l, m, n, o, ō, p, s, t, u, ū, v (r is left out since no words start with this letter).

He recommends that consonants be named consistently with a following ā: fā, gā, hā, kā, lā, mā, nā, pā, tā, vā, rā, sā.

As with many languages, writing was brought to Niue in connection with religion, in this case with Christianity by missionaries educated in Samoa.

Because the unmarked case is the absolutive, Niuean transitive verb constructions often appear passive in a literal translation.

Furthermore, first person non-singular (dual and plural) pronouns distinguish inclusive and exclusive forms, including and excluding the listener, respectively.

Note that the endings of the dual and plural forms resemble the numbers 2 and 3, ua and tolu.

Suppletion concerns closely related words (often singular and plural forms of nouns or verbs) which are based on very different forms, for example fano to go (used with a singular subject) and ō to go (used with a plural subject).

This is used for several purposes, including: An example of a whole-morpheme reduplication indicating a plural verb is molemole to have passed by, to be gone from mole to have passed by, to be gone[clarification needed]; an example of a whole-morpheme reduplication indicating a frequentative verb is molomolo to keep squeezing from molo to squeeze, to compress.