Fair warning, these are deductions made by the community based off patterns in his works, so we will never know for certain whether this was what the renowned author would have wished.
Overview
From its inception until the sundering of the Faithful and the King's men, the languages most beloved within Númenor were the elven languages, especially among the elites and nobles. This, along with Primitive Adûnayân's rather underdeveloped phonetics, paints a picture of a language originally utilized as a backup tongue, one that everyone can speak if need be due to their heritage but otherwise given little regard. This seems to have led to a simplistic (or perhaps foundational?) approach to the language, from its grammar to its words. Very strong rules with little deviation for maximum ease of understanding. For a semi-agglutinative language, it is easy to decipher, at times not unlike taking basic Lego pieces and attaching them to make something else.
Having been relegated to the background from the beginning of Númenor, the tongue necessarily developed a more vulgar feel to its sounds. However, it still seeks to emulate the
The words, too, are not only easy on average to figure out due to the heavy adherence to biconsonantal/triconsonantal formations, they attempt to be Onomatopoeic of the concept whenever possible (like the classic example karab for "horse", which conjures the sound of a horse gait). Even when the language became the tongue for everyone following the end of the Golden age of Númenor, it still retained the simplistic look towards its usage, the structure still heavily tilted towards logical understandability in contrast to the understanding via beauty interwoven through the elven languages, or perhaps the information density structured into Modern English. Fundamentally vulgar in tone, its speakers still developed and modulated its usage for an ease and fluidity of speaking that may rival Sindarin or Quenya, giving it a lyrically harsh feel to the language.
Biconsonantal
A-fortification:
– CaVC
– ai > ê
– Noun: baith > bêth “word” (< BITH).
– Agental suffix: -baith > -bêth “speaker” (< BITH), though in names (and proper nouns) only; cf.
Inzilbêth.
– aa > â
– Noun:
– Agental suffix:
– au > ô
– Noun: laukh > lôkh “bending” (< LUKH)
– Agental suffix: -laukh > -lôkh “bender” (< LUKH), though in names (and proper nouns) only.
Without syncope:
– Agental suffix
– Male, -ôn:
– Female, -ên:
– Common, -ân: magân “builder” (< MAG).
– Name / proper noun suffix:
– Male, -û: Nîlû “Man of the Moon”.
– Female, -î: Ûrî “Lady of the Sun”.
– Adjectival:
– katha “all”, pl. kathî (< KATH); placing stem vowel after the last consonant.
– VCVCV:
– Participle:
– Passive, -ân: zabathân “humbled” (< ZABATH).
– Dual suffix -at: azra-at > azrât “pair of seas” (< ZAR).
Triconsonantal
A-fortification:
– CVCaVC
– ai > ê
– aa > â
– au > ô
– Adjective: burauda > burôda “very heavy” (< BURUD).
With syncope:
– Agental suffix -ân: phazgân “conqueror” (< PHAZAG).
– Name / Proper noun suffix:
– Male, -û: karbû “stallion”.
– Female, -î: karbî “mare”.
– Adjectival:
– dulgu “black”, pl. dulgî (< DULUG); placing second vowel after the last consonant.
– VCVCCV: izindi “true” (< ZINID).
– Dual suffix -at: huznat “pair of ears” (< HUZUN).
– When the second-to-last syllable is short (has a short vowel and ends in one consonant).
Without syncope:
– Dual suffix -at: târikat “pair of pillars” (< TARAK).
– When the second-to-last syllable is long (has a long vowel, diphthong or ends in two consonants).
Rules
Onomatopoeia.
This means that when it comes to animals, sounds, or various objects with sounds associated with them, their name should evoke memories of that sound (such as karab for horse, which evokes the thought of a horse galloping).
Exceptions to the rule is where the creature or object is one naturally shunned and rather not talked about, then it tends to have a name identical or nearly so in sound to an elvish word for it (such as uruk for “orc”).
A corollary to this is the association of -u- and -ô- with stronger/darker themes, while -i- and -ê- tend to be with lighter, more feminine themes.
Two-vowel Minimum.
While a word can end up with as little as one consonant, the word must always have the minimum of two vowels in a word, even if it is in the form of a long vowel. Some examples are katha (“all”), ûri (“sun”), or pâ (“hand”).
No more than three consonants!
Adûnaic is a composite bi/triconsonantal word system. In other words, the base word cannot have more than three consonant sounds. The only way to bypass the limit is to either form a word from multiple words or add a suffix onto the base word (such as agental and verbal suffixes).
Example: pharaz + -ôn (“gold” + adjectival suffix) à pharazôn (“golden”). huzun + -dâ (“ear” + verbal suffix) à huznudâ (“to hear”). Katha + phazag- + -ân (“all” + “to rule” + agental suffix) à kathuphazgân (“conqueror, (lit.) all-ruler”).
Standalone Suffixes.
Words meant to be used as a suffix should by default be only one short vowel, (unless you have an -e- or an -o-, which in that case it’s long by default).
If used as a standalone word, the base vowel must be lengthened if necessary.
Occasionally, you may want to forge a triconsonantal word whose base and variable vowels do not agree, and cannot be explained away as a-fortification (i.e. burôda, “(very) heavy”) or some other normal process. In such a process, it is recommended to insure that in base form, the two vowels will form a recognized Adûnaic diphthong (e.g. târik, “pillar” à âi). The one exception to the rule is words with a base vowel -i- and secondary vowel -a- (e.g. minal, zidar, “sky” and “poise” respectively).
Nouns from Verb Roots
Unconfirmed, but nouns adapted from verbal roots may require a prefix of sorts, (e.g. -a). This is based off of the formation of azûl and adûn from the hypothetical verbal roots √ZUL (“rise”) and √DUN (“sink”).