The terms ‘number’ and ‘numeral’ are often confused: One is a number, but 1 is a numeral. Added to this, numerals in typography are referred to as ‘figures’. (No one said this would be easy!)
We frequently encounter figures when wrestling with typography: telephone numbers, dates of birth, financial data, fractions… the list goes on. Well designed typefaces include ‘old style’ figures (1234567890) in addition to ‘lining’ figures (1234567890). Lining figures were originally designed to be used in conjunction with capitals; old style (or ‘lowercase’) figures blend in better with text settings given their ascenders (6, 8) and descenders (3, 4, 5, 7, 9).
In addition to old style and lining figures, a thoughtfully designed typeface will include ‘proportional’ and ‘tabular’ figures. Proportional figures, as the name implies, have differing widths (a 1 is narrower than a 9), and are designed to fit together like letters. Tabular figures, on the other hand, are designed for tabular data and designed to be mono-width.
When setting figures within a paragraph of text – a date of birth, for example – old style proportional figures are the ideal choice. When setting numerical data, however – an annual report, for example – lining tabular figures would be a better choice.