12.19.1 Alphabet and accents
The Welsh alphabet consists of twenty-eight letters, alphabetized as a b c ch d dd e f ff g ng h i j l ll m n o p ph r rh s t th u w y. The letters k and v are very frequent in medieval texts but are now obsolete.
Rh counts as a separate letter at the start of a word or syllable only, i.e. after a consonant but not a vowel: route comes before rhad ‘cheap’, cynrychioli ‘to represent’ before cynrhon ‘maggots’, but arholi ‘to examine’ before arian ‘money’; w is usually, у always, a vowel.
All vowels (including w and y) may take a circumflex. Acute, grave, and diaeresis are also found: most frequent are á in final syllables (casáu ‘to hate’) and ï before a vowel (copïo ‘to copy’). The letter with the diaeresis always precedes or follows another vowel.
A word consisting of an apostrophe followed by a single letter must be set close up to the preceding word:
12.19.2 Word division
Do not divide the digraphs ch, dd, ff, ll, ph, rh, th. Note that ng is indivisible when a single letter, but not when it represents n + g: this happens most frequently in the verb dangos ‘to show’ and its derivatives, compounds ending in -garwch or -garwr (e.g. ariangarwr ‘money-lover’), place names beginning with Llan- (Llangefni, Llangollen), and in Bangor. Thus cyng-aneddol but dan-gosol.
Do not divide ae, ai, au, aw, ayw, ei, eu, ew, ey, iw, oe, oi, ou, ow, oyw, wy, yw, and other combinations beginning with і and with w when this letter is a consonant. The presence of a circumflex or an acute does not affect word division, but it is legitimate to divide after a vowel bearing the diaeresis, as also after a diphthong or triphthong before another vowel. Thus barddoï-aidd ‘bardic’, gloyw-ach ‘brighter’, ieu-anc ‘young’.
Generally, take back a single consonant other than h, except after a prefix (especially di-, go-, tra-): g-l but s-gl (and so similar groups). A suffix beginning with і plus a vowel must be broken off: casgl-iad ‘collection’.
It is always safe to divide l-rh, ng-h, m-h, п-h (but n-nh), n-п, n-rh, r-r, and after a vowel r-h. Initial gwl-, gwn-, gwr-, and their mutated forms must not be divided, since the w is consonantal: gwlad ‘country’, (hen) wlad ‘(old) country’, gwneud ‘to do’, (ei) wneud ‘to do (it)’. Gwraig ‘woman’, (y) wraig ‘(the) woman’, cannot be divided.
12.19.3 Mutations and other changes
As in Irish Gaelic, initial consonants are replaced in certain grammatical contexts by others in a process called mutation: cath (‘cat’) but fy nghath (‘my cat’), ei gath (‘his cat’, ei chath (‘her cat’). Caerdydd (Cardiff), Dinbych (Denbigh), Gwent give i Gaerdydd (‘to Cardiff’), yng Nghaerdydd (‘in Cardiff’), і Ddinbych (‘to Denbigh’), yn Ninbych (‘in Denbigh’); i Went (‘to Gwent’), yng Ngwent (‘in Gwent’). ‘Oxford’ is Rhydychen, but ‘from Oxford’ is o Rydychen. The full range of mutations is b to f or m; c to ch, g, or ngh; d to dd or n; g to zero or ng; ll to l; m to f; p to b, mh, or ph; rh to r; t to d, nh, or th.
Initial vowels may acquire a preliminary h (offer ‘tools’, ein hoffer ‘our tools’) and changes of stress within a word may cause h to appear or disappear and double n or r to be simplified: