The Marquesan languages have undergone quite a few interesting sound changes. The velar nasal (“ng” in “singing”) is completely gone in most variants, the /f/ only exists on one island, the “r” and “l” has disappeared from many words in all variants, to the point where even the word for “language” – ” ‘eo’ ” lost its /r/ or /l/.
The language(s) also have a number marker known as the “paucal”, which indicates a few, or several of something. It has dual, and plural markers just like typical Polynesian languages.
The verbal structure is also very typical of Polynesian languages, it has the imperfective and perfective aspects, tense (like the past, present, imperative), and also mood, such as the desiderative. The desiderative mood plays a subjunctive role in Marquesan, but rather than being a tense, it is a mood in this language. Another thing possibly unique to Marquesan is what’s called “the caveat mood”, this mood is simply used to warn, strongly suggest, or to make someone aware of something, it has two markers, one of a weaker warning, and another which is stronger. It could be somehing like “lest” or “unless”, “look at the road, lest you (want to) crash”.
Check these resources out to learn more about the Marquesan languages, and this LangShack video on the subject.
“Grammaire et dictionnaire de la langue des Îles Marquises”: Mgr Rene Ildefonse Dordillon’s Marquesan language dictionary & Grammar (Société des études océaniennes, Pape’ete, 1904 – reissued 1999) (in French)
Mutu, M., & Tekìtutoua, B. (2002). Ùa Pou: Aspects of a Marquesan dialect.