oldstyle figures (osf)

Numbers that have different heights, some aligning to the baseline, some below. Oldstyle figures harmonize well with lowercase letters. Using oldstyle figures helps keep the numbers from standing out too much and disturbing the overall flow of the typography on the page. Oldstyle figures can be proportional or tabular. When the different figure sets are built-in as OpenType features, certain (older) operating systems and applications will only be able to access the default figures, most often the tabular lining figures. See Figuring Out Numerals on The FontFeed.