In typography and penmanship, the baseline is the line upon which most letters "sit" and under which descenders extend.

In the example to the right, the letter 'p' has a descender; the other letters sit on the (red) baseline.

Most, but not all typefaces are similar in the following ways as regards the baseline:

• Lined or tabular figures (see Arabic numerals), and capital letters sit entirely above the baseline.
• The following text figures have descenders: 3 4 5 7 9.
• The following lowercase letters have descenders: g j p q y.
• Glyphs with rounded lower extents (0 3 5 6 8 c C G J o O Q U) break the baseline slightly to create the optical illusion that they sit on the baseline.

The vertical distance of the base lines of consecutive lines in a paragraph is also known as line height or leading, although the latter can also refer to the base-line distance minus the font size.

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