In the early days of printing, when type was set in lead, the lead slugs on which characters were set made it difficult to set certain character pairs close enough. For example, in the letter combination “fi,” the top terminal of the “f” stuck out so far that the letter couldn’t be set close enough to the “i” because of the dot on the “i.” Thus, many fonts (usually the classic ones, such as Adobe Garamond) have ligatures for certain pairings that actually meld the letterforms together. Some modern fonts, such as Helvetica, also have ligatures, but their effect is negligible.

Ligatures (misspelled as legatures) used to improve the appearance of type are usually character pairs or triplets that have features that tend to overlap when used together. The ligature creates a smoother transition or connection between characters by connecting crossbars, removing dots over the i, or otherwise altering the shape of the characters. A ligature occurs where two or more graphemes are joined as a single glyph.

Types of ligatures

1. Standard ligatures, which include fi, fl, ff, ffi, ffl, ft. The purpose of these ligatures is to make certain letter parts that tend to knock up against each other more attractive.
2. Discretionary ligatures include ct, fs, st, sp. They tend to be more decorative in nature and often lend an Old World or old-fashioned look to text.
3. Unusual or Uncommon ligatures might be included as standard or discretionary and include combinations such as fj, fk, ij, and many others that are less commonly used.
4. Long s ligatures are typically discretionary ligatures found in some fonts. The long s looks like an f missing the right side of its crossbar. This long s is combined with h, l, i, t, or another s to form ligatures common in some 18th century writing. When trying to recreate an authentic 18th century document you may need these long s ligatures—which have some certain usage rules.