Of course, things get a little more complicated when you dig a little further into Kryptonian's vowel system. Here's "everything you wanted to know but were afraid to ask" on Kryptonian vowels...
The Basic Vowels
When learning the vowels, it is important to learn their placement on the vowel chart (fig.1) as this will also help you learn verb tenses, pluralization forms, adjective comparisons, and gender-shift on gendered nouns. The vowels (found in the basic alphabet) are listed again here for convenience with the addition of y.
Please take note that the vowel y is considered a "raised" variant of the vowel e, and, therefore, should be treated as though it were in the same position on the vowel chart when it comes to gendered nouns.
There are two Kryptonian diphthongs represented with ligatures (ligatures are where two or more letters are joined together into one symbol).
Kryptonian has special characters for rhoticized vowels (fig. 3). In essence, these characters are ligatures of a sort from the combination of a vowel preceding the approximate r (r).
From the chart, you will notice that there is no rhotic version of the raised vowel y (which never occurs before r).
You will also notice that U becomes r on the chart which is the same character for / r /. In fact, the symbols are one and the same, and it is only listed here for clarity.
In fact, when preceding or following a consonant, r is syllabic as can be seen in rT [ ɹ̩θ ] (Earth) and ukr [ u.kɹ̩ ] (father). It is only when preceding a vowel that r loses its syllabic quality, e.g., rOZ [ ɹa͡ʊʒ ] (knowledge).
The Letter i and "You"
The letter i in Kryptonian, when preceding a vowel, loses its vowel quality to become the consonant [j] (as the "y" in English "you" … you see what I did there?). In this situation, the letter is written as a diacritic above the following vowel as shown below. The combining can occur over any vowel including the rhotic vowels and the ligatures.
Note that ý is never written on its own in Kryptonian, and while technically it is a consonant, it really is just an allophone for /i/ and so it appears on this page and not the consonants page.
Also note that í and Ý are exceedingly rare combinations in Kryptonian.
The Vowels and Gendered Nouns
The Kryptonian language reflects natural gender in words through the use of its vowels. Please note that this gender is not word classification like you find in languages such as Spanish or German where all nouns carry a "gender", but, rather, Kryptonian word gender only affects nouns that describe an object that actually has (or implies, e.g. an android) a natural gender.
The gender of a gendered noun is determined by the first vowel of the word. The vowel may be "shifted" left or right on the vowel chart to change the gender of the word (fig. 2). For example, / aonah / (offspring) can become / inah / (daughter) or / unah / (son). Dictionaries list gendered nouns in the neutral form with the gender-indicative vowel underlined.
Formal speech defers to the neutral gender whenever possible, while the gender-indicative forms are usually reserved for familiar speech. However, gender may be indicated in formal speech when it is needed for clarity—usually in 3rd person contexts or when speaking to more than one person. This formality applies in both directions in the social heirarchy, i.e., an underling would not use gendered speech with his superior nor vice versa.
The raised e vowel, y is considered to be a gender-neutral vowel, but should not be treated the same as the other vowels. y carries with it not so much a sense of gender-neutrailty as it does gender- all-inclusiveness. In gendered words, it is very uncommon (and less socially acceptable) to shift this vowel to a single-gendered entity (/ e / or / o / ). This vowel can also be seen in some non-gendered words that may have carried gender in their original form, e.g., ZRyGRas (city). This is evidenced by the fact that some of these words can be found in older texts, usually poetic in nature, in a gender-specific form, e.g., Kor-Fehn's epic poem, ZRoGRas, universally translated to "City of Men."