Leafy: Vocabulary Builder for Mac

Look up words without losing your place
Leafy is a lightweight macOS utility for readers who don't want to break their flow to check a definition. Press ⌥A, drag a box around any word on your screen — in a PDF, an ebook, a locked document, or an image — and get an instant definition or translation without switching windows or opening a browser tab.
A vocabulary that builds itself
Every word you look up is saved automatically to your personal library. There's nothing to organize by hand: just keep reading, and a searchable, sortable wordlist grows in the background.
Features

⌥A everywhere — works over PDFs, ebooks, images, and locked documents
Automatic saving — every lookup is added to your library instantly
Search & sort — find any word you've saved, anytime
Export — send your library to CSV or Excel
Import — bring an existing list in with a standard CSV or Excel template
PopClip support — look words up straight from the PopClip bar
8 languages, with more on the way
Privacy-first — no account required, no tracking; words stay on your Mac

Leafy is free while in beta and requires macOS 14 or later.