Every set, folder, word and task belongs to one language pair. The lists you see are filtered by the pair you are working in, so a set made in English through Russian is simply not on the screen while you are in English through Spanish.

Removing a pair therefore empties everything that lived in it. The sets, the folders and the words stay in your account exactly as they were — nothing is deleted and nothing is lost — but nothing filters them into view any more, and the platform does not warn you before you remove the pair.

To get them back, add the pair again. Settings → Education → choose the same source and target language → press the plus. Everything created in that pair is on the screen again, unchanged.

Two things worth knowing before you remove a pair:

• Check what is in it first. Switch to the pair and look at your Words and Tasks pages. Whatever is there is what will disappear from view.
• Pairs belong to an account, not to you. If you have both a teacher and a student account, removing a pair on one side leaves the other side alone.

Adding someone else’'s set to your library also adds the pair that set needs, so a pair can reappear on its own.