Cardiau Cymraeg is a Welsh vocabulary app for iPhone: the 1,000 Welsh words you’ll use most, learned a few at a time, in Welsh or English. This page covers the decisions behind it, for anyone planning an app that has to work in Welsh.
Cardiau Cymraeg was not written in English and translated later. Every label, button and message exists in Welsh and in English, and neither language is a fallback for the other. On first launch the app follows the phone’s language. After that it keeps the one you choose, and switching takes effect straight away, without a restart.
Most of the work is in the details a Welsh speaker notices when they’re missing.
The answer times read 2 ddiwrnod, 2 fis and 1 flwyddyn, worked out from Welsh rules rather than an English plural.
Type gath, nghath or chath and search finds cath. Accents are optional, so dwr finds dŵr.
The language switch shows each name in its own language, so either can be found from the other. Welsh words are tagged as Welsh in the app’s text.
The app’s site has a full Welsh page, with its own Welsh-first share image, so a link shared in Welsh previews in Welsh.
The Welsh on this page and in the app has not yet had a native speaker’s review. This section describes the engineering that lets Welsh work properly.
Nothing in the deck was made up. The order of the words, their meanings and the forms search understands all come from open, citable sources, each credited under its licence.
| Used for | Source | Licence |
|---|---|---|
| Word order and part of speech | Yr Amliadur, frequency lists for contemporary Welsh, Cardiff University | CC BY-SA 4.0 |
| English meanings | English Wiktionary’s Welsh entries, via kaikki.org. Shortened, some rewritten by hand | CC BY-SA 4.0 |
| Gender, capitals, word forms for search | Lecsicon Cymraeg Bangor, Prifysgol Bangor | CC0 1.0 |
Two of the three licences ask for the same openness back, so the word list itself is published free under CC BY-SA 4.0, for anyone to download and reuse: get the word list.
The words come most common first, up to 20 new ones a day, so the first week covers the words you’ll meet most.
Every one of the 1,000 words has a recording you can play. Most use AI voices, and each one was chosen by ear, word by word.
A recording that has to load after you tap feels broken. So the app uses look-ahead, an open source Swift package Async Digital wrote, to keep the recordings for the cards around the one you’re on loaded and ready, and to let the rest go.
You answer Hard, Good or Easy, and the app works out when to show that word again: soon if it’s shaky, days or months later once you know it. Each answer shows its return time before you choose.
That timing comes from FSRS-6, an open scheduling method published by Open Spaced Repetition. We ported it from their reference implementation, py-fsrs, rather than inventing our own, so the app’s behaviour can be checked against a published original.
There is no account and no analytics. The app collects no personal data, your progress stays on your iPhone, and it works without an internet connection. For a learning app that is a design choice, and it also keeps the privacy policy short.
Async Digital built Cardiau Cymraeg with Claude, Anthropic’s AI model, writing much of the code. We set the decisions on this page, chose the sources and the voices, and decided what each change had to pass before it shipped.
Async Digital builds apps like this one. Read what the Welsh Language Standards ask of apps and websites, see Cardiau Cymraeg, or get in touch at info@async-digital.com.