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. Standard ligatures may include fi, fl, ff, ffi, ffl, ft.

When would you use a ligature?

The only time ligatures are mandatory is when you have an actual overlap between the letters f and i. Check this combination in the bold and italic styles too. The font in the first row, Concourse, has an fi combination that doesn't collide. That font will work fine without ligatures.

How are ligatures used today?

For surgery, ligatures are used to tightly occlude blood vessels. Ligation of solitary vessels, or multiple vessels within a pedicle (mass ligation), is used virtually daily in practice for ovariohysterectomy, castration, amputation, splenectomy, and lobectomy.