Old Style Figures
The numbers we use every day in the western world are called Arabic numerals. They were first discovered in Algeria by the Italian mathematician Fibonacci. There are different ways of setting type with these figures.
Lining figures are most common. They don’t fit very well in running text. It’s like they’re written in ALL CAPS. They stand out too much.
The second way of setting numerals in body copy is to use proportional old style figures.
Proportional old style figures are an elegant addition to your typographic layout, if they’re available in the font you’ve chosen. They’re easier to read and flow better in running text. They look like they have ascenders and descenders like the rest of the glyphs in the text.
Tabular old style figures are identical to the proportional old style figures, except that their letter-spacing is designed to accomodate columns of text. As you can see, the proportional figures don’t align well in columns. The tabular ones do.
How do I use them?
To use old style figures, find the OpenType setting in your Paragraph Style or in the OpenType panel.
Old style figures have become much more common with the use of the OpenType font format. This format allows for 1024 glyphs in the font. Before that, the common limit was 128 glyphs, so there was just no room for them.