The Hawaiian alphabet is short. In comparison with the English set of 26 letters, Hawaiian has only 13. 5 vowels, 7 consonants, and the ‘okina, written as ‘. There is the macron used to mark long vowels in the Hawaiian language, but these vowels carrying macrons are not considered separate letters.
With such a short alphabet, one would expect Hawaiian to have a very small phonological inventory. And they would be correct. The Hawaiian language is known for its extremely small phonological inventory, with 8 consonant phonemes, and depending on how you define vowel phonemes, 5 or 25 vowel phonemes. Its syllable structure is also quite simple — no consonant clusters, and a (C)V(V) structure. Famously, this has resulted in the translation of “Merry Christmas” as Mele Kalikimaka in Hawaiian. That is right, the Hawaiian language does not have an “s” sound, and does not really distinguish between the sounds “k” and “t”.
With these facts provided, one would be curious and ask, why?
In fact, looking around Hawaiian’s Polynesian cousins, we see a rather similar pattern in unusually small phonological inventories. The Tongan language has 12 consonant and 5 vowel phonemes, while the Samoan language has 10 consonant and 5 (and when factoring in vowel length, 10) vowel phonemes. The latter language does not distinguish between “k” and “t” sounds, instead, uses it in different registers of speech (think informal and formal). Similarly, Tokelauan also has 10 consonant and 5 vowel phonemes, but does distinguish between “k” and “t” as separate phonemes.
So it does seem that a small phonological inventory is a pattern within this branch of the Polynesian languages. For this particular branch, these languages have essentially lost the distinction between voiced stops (think “g”, “d”, “b” sounds) and voiceless stops (think “k”, “t”, “p” sounds). As such, these languages tend to have only voiceless stop consonants.
Another thing that Hawaiian has lost are the sounds /ʧ/ and /ʤ/. These sounds have become “fused”, or more formally speaking, merged, with the “k”, “t”, and “p” sounds, and the glottal stop ‘. Now, this set of glottal stops and other voiceless stops has its own history of sound changes behind it as well, which we will cover later. But there has to be some point in the history of the Polynesian languages in which such sounds have merged into the voiceless stops.
We also note that the Hawaiian language lacks fricative and sibilant consonants, like “f” and “s” respectively. This reveals yet another probable merger of consonant sounds, this time with the “h” sound, with the theory that these consonants generally let air pass through a narrow opening with audible friction. The “h” sound might take less effort to articulate compared to the “f” and “s” sounds, making a merger into the “h” sound more probable than the other consonants. Other notable mergers are the “ng” sound into “n”, and “r” sound into “l”, although allophones do exist, like it does for /v/ with /w/.
Lastly, there is the historical shift in the consonants “t”, “k”, and the glottal stop. At some point in Polynesia’s linguistic history, the “k” sound shifted towards the glottal stop, and some Polynesian languages have undergone the shift from “t” to “k” as well.
These sound changes and mergers over time has resulted in what Hawaiian sounds like today. A weird set of consonants and vowels that lacks some of the sounds one would likely expect in a language, like the “s” sound, and phonemic “k”, “t”, and “p” sounds. Remember, the “k” and “t” sounds are not phonemically distinguished in Hawaiian. With it, comes a highly truncated alphabet half as long as the alphabet we use in English. Hopefully this post has introduced how Hawaiian has probably got to where it is today, although some changes might require more digging into in more linguistic papers and literature.