Introduction
Vocal Tract
The nereidic vocal tract developed from an organ that was originally used as a siphon, when their ancestors still lived in the oceans of Nereus. It now functions as a primary component of their respiratory system and is involved in other bodily functions including waste excretion and copulation. The inside of the siphon is called the “mantle cavity” and is extremely flexible allowing for a variety of articulations and speech sounds. The most basic places of articulation include labial (the lips of the siphon), coronal (the middle area of the mantle cavity), dorsal/velar (the back part of the mantle cavity where the velum separates it from the oesaphagus), and glottal (the glottis or vocal chords at the “end” of the vocal tract). Only the labial, dorsal, and glottal parts of the nereidic vocal tract are capable of complete closure.
Consonants
The consonant sounds that nereids can produce are much more restrictive compared to humans. Notably, cavital stops, the nereidic equivalent of human alveolar stops, are impossible. Similarly, the trill and tap/flap manners of articulation are impossible for the nereidic vocal tract.
| Labial | Precavital | Medicavital | Retrocavital | Velar | Glottal | |
| Rostral Stop | m̥ m | ŋ̊ ŋ | ||||
| Rostral Fricative | m̥͋ m͋ | ŋ̥͋ ŋ͋ | ||||
| Plosive | p b | k g | ʔ | |||
| Sibilant | s z | ʂ ʐ | ɕ ʑ | |||
| Non-Sibilant | ɸ β | θ ð | ɻ̊˔ ɻ˔ | ç ʝ | x ɣ | h ɦ |
| Glide | w | ɹ | ɻ | j | ɰ | |
| Lateral Fricative | ɬ̼ ɮ̼ | ɬ ɮ | ꞎ ɭ˔ | ʎ̝ | ʟ̝ | |
| Lateral Glide | l̼ | l | ɭ | ʎ | ʟ |
Vowels
Nereidic vowels are often articulated in two different areas of the mantle cavity at once, resulting in acoustic effects similar to what might be called “rhoticization” and “lateralization” in human phonetics. This adds an extra dimension to nireidic vowels beyond the human system of frontedness, height and roundedness. This fourth dimension is dependent on the openness of the front articulation or precavital constriction, sort of like a internal secondary “rounding” feature, which results in open (no constriction), rhotic (partially constricted), and lateral (fully constricted) articulations. This has a huge effect on the third formant of vowels, where the more constricted the articulation, the lower the third formant. This third formant is thus important for identifying nereidic vowels, particularly when compared to most human vowel systems, where the first and second formants are sufficient. From a human perspective, the rhotic vowels can often be thought of as a syllabic approximant or non-sibilant fricative with the added dimensions of vowels, and similarly the lateral vowels as a syllabic lateral approximant with added dimensions. This added dimension of front constriction is important for describing the phonetic and phonological systems of nereidic languages.
| Front | Central | Back | ||
| Open | High | i y | ɨ ʉ | ɯ u |
| High-Mid | e ø | ɘ ɵ | ɤ o | |
| Low-Mid | ɛ œ | ɜ ɞ | ʌ ɔ | |
| Low | æ | a | ɑ | |
| Rhotic | High | i˞ y˞ | ɨ˞ ʉ˞ | ɯ˞ u˞ |
| High-Mid | e˞ ø˞ | ɘ˞ ɵ˞ | ɤ˞ o˞ | |
| Low-Mid | ɛ˞ œ˞ | ɜ˞ ɞ˞ | ʌ˞ ɔ˞ | |
| Low | æ˞ | a˞ | ɑ˞ | |
| Lateral | High | iˡ yˡ | ɨˡ ʉˡ | ɯˡ uˡ |
| High-Mid | eˡ øˡ | ɘˡ ɵˡ | ɤˡ oˡ | |
| Low-Mid | ɛˡ œˡ | ɜˡ ɞˡ | ʌˡ ɔˡ | |
| Low | æˡ | aˡ | ɑˡ | |