What is meant by printing a book in the vernacular?​

An incunable, or sometimes incunabulum (plural incunables or incunabula, respectively), is a book, pamphlet, or broadside printed in Europe before the 16th century. Incunabula are not manuscripts, which are documents written by hand. As of 2014, there are about 30,000 distinct known incunable editions extant, but the probable number of surviving copies in Germany alone is estimated at around 125,000. Through statistical analysis, it is estimated that the number of lost editions is at least 20,000. Around 550,000 copies of around 27,500 different works have been preserved worldwide.

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