Iha is the main language of the Onin peninsula, found at the far western end of New Guinea. Iha is closely related to Mbaham, and perhaps related to the language of the Karas islands. There are good indications that these languages are the westernmost members of the Trans New Guinea family (unlike Mor, the other Papuan language of the area).
An affricate [dʒ] occurs, but is possibly better analysed as a /d̪/ + /j/ sequence. Other stop + glide sequences, [pj-], [k͡pj-] and [kj-] (< /qj-/) are attested, along with their prenasalised equivalents, but [t̪j] is not.
The voiceless stops lenite intervocalically; /p/ → [β], /t̪/ → [ð] (occasionally), /q/ → [ɣ]~[ʁ], and even (rarely) /k͡p/ → [w]. This collapses a number of phoneme contrasts; while /p/ and /β/ contrast word-intially, morpheme internally it is not possible to know whether [β] represents an underlying stop or a fricative. The prenasalised stops have also been heard to lenite: /nŋ͡mg͡bit̪/ 'afternoon' has been heard as [nɪ̆ˈw̃it̪].
The seven vowels only contrast in open syllables; in closed syllables a five way contrast between [ɪ ɛ a ɔ ʊ] is attested. Schwas and other short versions of these vowels are found in epenthetic syllables.
Syllables in Iha are maximally CCVC in shape; the second C in an onset cluster is restricted to liquids and glides, and the prenasalised stops and fricatives do not occur in coda positions. With some CC clusters an epenthetic vowel is inserted.
Verbs are highly polysynthetic in Iha; one example of a highly-inflected verb is given below (presented phonetically, phonemically, and orthographically):
[miɣɛ qɔɻɛt̪ nɛ̆wɛβjə̆mja:njat̪ə̆n̪an̪wɛɻad̪ɛmbɪçt̪ə̆βjeβɔn̪ pja]
/mikɛ qɔɻɛt̪ nwɛpjmjan̪jat̪n̪an̪wɛɻad̪ɛmbiħt̪pjβɔn̪ pja/
'He kept on eating all sorts of things, for an extended time, again and again, and I witnessed it multiply and repeatedly, so don't doubt me.'
The glosses have the following meanings: