The newly revised Ithkuil has 45 consonants and 13 vowels. At the left of each cell in the table below is the phoneme, and at the right its transliterated representation if it is not written the same in IPA as in romanized Ithkuil. The consonants are as follows:[1]
| Labial | Dental | Alveolar | Retroflex | Post- alveolar |
Palatal | Velar | Uvular | Glottal | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| central | lateral | ||||||||||
| Nasal | m | n̪ n | ŋ ň | ||||||||
| Plosive | voiced | b | d̪ d | ɡ | |||||||
| voiceless | p | t̪ t | k | q | ʔ ’ | ||||||
| aspirated | pʰ | t̪ʰ tʰ | kʰ | qʰ | |||||||
| ejective | pʼ | t̪ʼ tʼ | kʼ | qʼ | |||||||
| Affricate | voiced | d͡z ż | d͡ʒ j | ||||||||
| voiceless | t͡s c | t͡ʃ č | |||||||||
| aspirated | t͡sʰ cʰ | t͡ʃʰ čʰ | |||||||||
| ejective | t͡sʼ c’ | t͡ʃʼ č’ | |||||||||
| Fricative | voiced | v | ð dh | z | ʒ ž | ||||||
| voiceless | f | θ ţ | s | ɬ ļ | ʃ š | ç | x | χ xh | h | ||
| Approximant | l | j y | w | ʁ̞ ř | |||||||
| Flap | ɽ r | ||||||||||
/m n̪ ŋ l ɽ/ can be syllabic. All consonants except /j w ʔ/ can be geminated; when geminated, h is a bidental fricative or a voiceless pharyngeal fricative (ħ), and ɽ is an alveolar trill. In a future revision of the language, Quijada has noted that cʰ, c’ čʰ, č’, kʰ, k’, ļ, pʰ, p’, q, qʰ, q’, ř, tʰ, t’, and xh will be eliminated, x will be pronounced /x/~/χ/, /ɬ/ will only be an allophone of word-initial /l̥/ (voiceless alveolar lateral approximant) and be written as hl, ň will be written as n before k, g, or x, and dh will instead be written as ḑ, as in the 2004 version of Ithkuil (this phoneme can optionally be written as đ or ḍ, but ḑ is preferred).
The 13 vowels of Ithkuil are as follows:[1]
| Front | Central | Back | |
|---|---|---|---|
| Close | iː î | ʉ~y ü | uː û |
| Near-close | ɪ i | ʊ u | |
| Close-mid | eː ê | oː ô | |
| Mid | œ~ø ö | ə ë | |
| Open-mid | ɛ e | ɔ o | |
| Open | ä a | ɑ â |
/ɪ ʊ/ are pronounced [i u] when they precede another vowel, and when at the end of a word. /ɛ ɔ/ are pronounced [e o] when they precede another vowel, excepting /ɪ ʊ/.
In a future revision of the language, Quijada has noted that ê, î, ô, and û will be removed to allow for easier memorization. a will be pronounced /a/, e will be pronounced /ɛ/~/e/, i will be pronounced /ɪ/~/i/, o will be pronounced /ɔ/~/o/, and u will be pronounced /ʊ/~/u/, â will be written as ä to be consistent with the other vowels and pronounced as /ɑ/~/ɒ/, and ë will be pronounced /ə/~/ɤ/, except when unstressed at the end of the word, where ë will be pronounced /ɯ/ to differentiate it from unstressed word-final -a.
The diphthongs in Ithkuil are /äɪ̯/, /ɛɪ̯/, /əɪ̯/, /ɔɪ̯/, /ø̞ɪ̯/, /ʊɪ̯/, /äʊ̯/, /ɛʊ̯/, /əʊ̯/, /ɪʊ̯/, /ɔʊ̯/, /ø̞ʊ̯/. All other sequences of vowels are pronounced as separate syllables. The grave accent is used to indicate the vowel sequence is not a diphthong. It should be noted that the grave and acute accents are used for stress. In a future revision of the language, circumflex accents will be used for stress, but grave accents will not be used for stress, and will only be used to indicate the vowel sequence is not a diphthong, so that the rules for marking stress are simplified.