Welsh orthography

[a] The letters ⟨k, q, v, x, z⟩ are sometimes used in technical terms, like kilogram, volt and zero, but in all cases can be, and often are, nativised: cilogram, folt and sero.

In this period, ⟨ð⟩ (capital ⟨Ð⟩) was also used interchangeably with ⟨dd⟩, such as the passage in the 1567 New Testament: A Dyw y sych ymaith yr oll ðeigre oddiwrth y llygeid, which contains both ⟨ð⟩ and ⟨dd⟩.

[7] The printer and publisher Lewis Jones, one of the co-founders of Y Wladfa, the Welsh-speaking settlement in Patagonia, favoured a limited spelling reform which replaced Welsh ⟨f⟩ /v/ and ⟨ff⟩ /f/ with ⟨v⟩ and ⟨f⟩, and from circa 1866 to 1886 Jones employed this innovation in a number of newspapers and periodicals he published and/or edited in the colony.

[4] However, the only real relic of this practice today is the Patagonian placename Trevelin ("mill town"), which in standard Welsh orthography would be Trefelin.

However, not all polysyllabic words with final stress are marked with the acute accent (Cymraeg "Welsh" and ymlaen "forward/onward", for example, are written with none).

The grave and acute accents in particular are very often omitted in casual writing, and the same is true to a lesser extent of the diaeresis.

If a vowel is not marked with a diacritic, its length must be determined by its environment; the rules vary a bit according to dialect.

Before nn and rr, vowels are always short: onn /ˈɔn/ (ash trees), ennill /ˈɛnɪɬ/ (to win), carreg /ˈkarɛɡ/ (stone).

In addition to the rules above, a vowel is long in the North before a consonant cluster beginning with s: tyst /tɨːst/ (witness).

Vowels are always short before consonant clusters: sant /sant/ (saint), gwallt /ɡwaɬt/ (hair), tyst /tɪst/ (witness).

While the digraphs ch, dd, ff, ng, ll, ph, rh, th are each written with two symbols, they are all considered to be single letters.

Automated sorting may occasionally be complicated by the fact that additional information may be needed to distinguish a genuine digraph from a juxtaposition of letters; for example llom comes after llong (in which the ng stands for /ŋ/) but before llongyfarch (in which n and g are pronounced separately as /ŋɡ/).