/ ˈkwɔːtəʊ; NAmE ˈkwɔːrtoʊ/ noun ( pl. -os ) ( technical )
1.
[ U ] a size of page made by folding a standard sheet of paper twice to make eight pages
2.
[ C ] a book with pages in quarto size
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WORD ORIGIN
late 16th cent.: from Latin (in) quarto (in) the fourth (of a sheet), ablative of quartus fourth.