The default font (font face) for each language is set in the Settings dialog box. The Fonts tab in the Book Settings dialog box shows a table of all the fonts used in the current book.
In each text box the gear icon (
) in the lower corner opens the Format dialog box. You can use it to change the formatting for that text box and any other text boxes that use the same language and style.
See Also: Font Features.
https://en.wikipedia.org/wiki/Font
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