Puzzle pieces are large enough to have words printed on them. Matching pieces have matching words from different languages, for example, French and English. The better you know the words, the quicker you can find the matching pieces. To make memorization less onerous.
Not so practical in cardboard because number of words limited, but computerized version of jigsaw puzzle allows you to easily switch to new sets of words, to as many as needed.
See link for screenshot of program I wrote to do this.-- flypaper, Oct 05 2004 Screenshot of computer version http://diyexperimen...w_Screenshot256.GIFSolve puzzle by dragging with mouse. [flypaper, Oct 05 2004, last modified Feb 14 2018] A fun, and easy way to learn. [+]-- Klaatu, Oct 05 2004 Nice! = Lindo! +-- Pericles, Oct 05 2004 i like! A bun for you.-- elfling, Oct 06 2004 croissant = croissant-- 2 fries shy of a happy meal, Oct 06 2004 Sorry, the links stopped working last fall because I changed ISP. Fixed now.-- flypaper, Aug 07 2009 random, halfbakery