I take notes when I read a book then review those notes and shrink them down further. Same for videos and articles online. Otherwise I'll just forget it within a few hours.
Take notes. Make sure you read them again a week later and reorganize them into smaller meaningful notes.
Those "Cards" can be re-read very quickly. And the simple notion of the few words a month later will replay and refresh the full context in your brain.
Works well if you don't have the time nor occasion to apply it
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Anki is great for foreign languages, chemical names, country flag to name mappings etc.