Four things, done properly, and nothing else competing for your attention.
You choose the dictionary
193 dictionaries from 64 publishers across more than 30 languages are built in, and every single link was checked against a live word page before it shipped. Monolingual and bilingual, English and well beyond it: French, German, Spanish, Italian, Portuguese, Turkish, Japanese, Korean, Chinese, Persian, Hebrew, Greek, Arabic, Russian, Hindi, Latin and more.
Yours missing? Paste any dictionary's web address with {word} where the word belongs, and Cardira will use it. Dictionaries you add work exactly like the built-in ones.
Spaced repetition that stays out of the way
Cardira uses a Leitner ladder. Remember a word and it moves up a box and comes back later; forget it and it comes straight back. Your list is simply your words, most overdue first.
Words you have fully learned move to a Learned list instead of cluttering the queue, and a daily cap on new words stops a big import flooding you.
Everything stays on your phone
No account. No sign-in. No server — we could not read your word list if we wanted to. Your words, your progress and your own dictionaries live on your device, and uninstalling deletes them.
Export a backup file whenever you like and import it on another phone. That export is also the only way to move your words between devices, so please do use it.
No permission prompts. No notifications.
Cardira never asks for location, contacts, photos, files, the camera or the microphone, and it never sends you a notification. Not "off by default" — not there at all.
On Android you can also share or select text in another app and send it to Cardira. It arrives ready to save, with the dictionary you used last already chosen.
Dark and light. Gold on charcoal by default, warm ivory in daylight. Both are built to WCAG AA contrast, every colour cue has a text or shape cue beside it, and the per-dictionary row tint can be turned down or off.