exercise for the reader

== English == === Etymology === From academic writing. One of the first known recorded occurrences of this phrase is in An Elementary Course of Mathematics by Thomas Stephens Davies, Stephen Fenwick, and William Rutherford from 1853. === Noun === exercise for the reader (plural not attested) Used other than figuratively or idiomatically: see exercise,‎ for,‎ the,‎ reader. (by extension) A matter left to the addressee's judgement to decide.