# What is a ligature?

Source: https://epubcc.com/glossary/ligature/ (updated 2026-11-04)

A ligature is a single glyph that joins two or three letters, such as "fi", "fl" or "ffi". Fonts use them for appearance; the underlying text should still be the separate letters.

## Why it matters when you convert a PDF to EPUB

In a PDF, a ligature can come out of text extraction as one special character (U+FB01 for "fi"), as nothing at all, or as the right letters, depending on the font's ToUnicode map. A converter should expand ligatures back into letters so that search, hyphenation and text-to-speech work in the EPUB.

How EpubCC handles it: ligatures and Arabic presentation forms are normalised with Unicode NFKC, so "fi" becomes "fi" in the EPUB. The normalisation is applied only to those characters, never to the rest of the text, so everything else stays exactly as the PDF encodes it.