Pick a topic and read through its Polish words, each with an English translation and part of speech. 22 topics, free, no sign-up. Polish spelling shown exactly as written. The app holds the full packs.
Watch Your Language puts Polish words like these in a widget on your iPhone Lock Screen and on your Apple Watch face. You see a handful of them every time you check the time, and the app schedules the repeats so the words you keep forgetting come back more often than the ones you already know.
You can add your own words too — from a photo, a page of notes or a spreadsheet.