[5] The vowels could combine into the following falling diphthongs:[6] 1. ending in /w/: /aw/, /ew/, /iw/, /ɨw/ ~ /əw/ 2. ending in /ɨ/: /aɨ/, /oɨ/, /uɨ/ 3. others: /ej/, /eʉ/ (and possibly /æj/, /æʉ/) The diphthongs /æj/ and /æʉ/, whose first component gradually changed into /a/, were originally allophones of /ej/ and /eʉ/, respectively, and no distinction between the two was expressed in Middle Welsh spelling, so their presence during most of Middle Welsh is not immediately observable.
The full opening to /aj/ and /aʉ/ may have been completed at some point in later Middle Welsh, possibly the thirteenth to fourteenth centuries.
Stress was placed on the penultimate syllable with some exceptions such as the causative verbs in -háu, e.g. sicrháu ('to make things secure' from sicr 'secure').
In terms of intonation, the tonal peak must have been aligned with the post-stress syllable, reflecting the earlier final stress of the late Brythonic period, since this persists even in Modern Welsh.
[9] The orthography of Middle Welsh was not standardised, and there is great variation between manuscripts in how certain sounds are spelled.
[10] In general, the spelling is both variable and historical and does not reflect some sound changes that had taken place by the Middle Welsh period, most notably the lenition.
There is a productive alternation between final syllables and non-final syllables known as mutation[13][14] or centring ([15]), which is by necessity triggered by the addition of any suffix and operates as follows: dwg 's/he leads' – dygaf 'I lead' hawl 's/he claims' – holaf 'I claim' marchawg 'horseman' – marchoges 'horsewoman' The centring mutation is due to a process of vowel reduction that operated earlier, in late Brythonic, when the stress was placed on the last syllable.
[9] Further, there are two types of alternations that are caused by following vowels (extant or lost) and are no longer entirely productive, but nonetheless very frequent in the morphology.
gwyr Ultimate a-affection is found, most notably, in the feminine forms of adjectives that do have gender declension, and it changes the stem vowels as follows:[16][17] The second type of affection is triggered by (typically) extant close vowels or semivowels in the following syllables, and is hence known as penultimate affection (in fact, it also reaches the antepenult in Middle Welsh).
Penultimate y-affection is a regular feature of verb forms with an ending containing y (e.g. the second person singular and plural in the present indicative).
Both it and other types of penultimate affection may also occur due to the addition of suffixes containing the respective vowels, e.g. in the plural of nouns.
deri cawr 'giant' – kewri Penultimate and ultimate affection may occur in one and the same form, e.g. castell 'castle' – pl.
Spirant mutation The spirant mutation replaced voiceless stops with fricatives: It occurs[21] after: a. the possessive pronoun for 3rd singular feminine possessors y 'her': penn 'head' > y phenn 'her head' b. the conjunction/preposition a 'and, with', the conjunctions no 'than', na 'neither, nor' and o 'if', the preposition and adverb tra 'over, very'.
c. the negative particles ny, na (note that these also cause the spirant mutation), the affirmative particles neu and ry, many prefixes such as go- and di- (note that these also cause lenition of the other mutable consonants) d. the numerals 3 and 6. e. the interrogative cw 'where?'
There is a definite article which precedes the noun phrase and has the form y- before a consonant and yr- before a vowel or /h/.
There are also singulative endings -yn (masculine) and -en (feminine), which produce singulars not only from collectives, but also from plurals: blew 'hair' > blewyn 'a hair'; llyc 'mouse' > llygot 'mice' > llygoden 'mouse'.
In the 3rd singular infixed pronoun, the allomorph -i/e is used after the words a, y, pan, tra and yny, while -s is used after ny, na, ry, neu, can, gwedy, kyt, o and pei.
The demonstrative pronouns may be proximal or distal and distinguish, besides the masculine and the feminine form, a neuter one, which, however, corresponds with the plural.
They are as follows: Some demonstrative adverbs are ynaeth 'then', yno 'there' (yna can mean both), ynoeth 'thither', yma(n) 'here', (y)velly 'so, thus'.
The inflection of the verb distinguishes two numbers and three persons, as well as a special 'impersonal' form, which is used in a way similar to a passive.
Of the different forms of the 3rd person of bot, yw, ynt follow the predicate, whereas (y) mae, (y) maent are placed in the beginning of the clause (and can alone mean 'where?'
Contrary to the example of caru, and unlike modern Welsh, the 3rd person singular preterite form most frequently ends in -wys or -ws, or in -s preceded by some other vowel as in -as, -es or -is, e.g. gallws 'was able'.
The /h/ of the subjunctives is in the process of disappearing after vowels and sonorants, but causes provection (devoicing and gemination) after voiced consonants: e.g. dycko corresponding to 1st person singular indicative dygaf 'bring'.
Some notable prepositions are a(c) 'with', am 'around', amcan y 'about', ar 'on', at 'to', can(t) 'with, by', ker 'near, by', ech 'out of', eithyr 'outside', erbyn 'by, for, against', gwedy 'after', heb 'without', herwyd 'according to', gerfyd 'by', hyt 'until', is 'below', mal 'like', o(c) 'from', parth 'towards', rac (/r̥aɡ/) 'for', (y) rwng (/r̥uŋ/) 'between', tan 'under' y 'to, for', tra(c) 'over, beyond', tros 'for, instead of', trwy 'through', y ('to', 'for', 'belonging to'), (y) tu (a(c)) 'towards', uch 'above', wrth 'at, by, for', y(n) 'in' (y before infixed pronouns), yr 'during, for'.
As in modern written Welsh, the VSO word order (Gwelod y brenin gastell: "Saw the king a castle") is not used exclusively in Middle Welsh, but irregular and mixed orders are also used: Y brenin a uelod gastell: ("[It was] the king that saw a castle").
The formal difference between the two is that a negative particle (ny/na) precedes the subject in the mixed order (thus Ny brenin a uelod gastell would mean "It was not the king that saw the castle", but precedes the verb in the irregular order (thus Brenin ny uelod gastell = "The king did not see a castle").
Furthermore, the mixed order could preserve the copula that originally participated in this cleft construction (Ys y brenin a uelod gastell).
Unlike modern Welsh, however, the irregular or 'abnormal' orders are much more common than the 'normal' one, even though they require an additional particle to be grammatical.
[46] There are two main variations: 1. with a subject or object 'fronted' before the verb (SVO or OVS) and followed by the particle a (causing lenition) – e.g. Arawn a eirch y wrogaeth instead of Eirch Arawn y wrogaeth 'Arawn asks for his homage';[47] 2. with an adverbial expression 'fronted' before the verb (AdvV) and followed by the particle y(d) (yd before a vowel; causing lenition) – e.g. Y Lynn Cuch y uynn hela instead of mynn ef hela y Lynn Cuch 'he wanted to hunt in Glynn Cuch'.
[48] Both particles may also be replaced by ry or yr.[49] When the verb of a sentence is a copula governing a nominal predicate (P), early texts preferred the order VPS, but PVS becomes more common in the bulk of Middle Welsh prose.