The fully closed, rounded part of a letter.
Definition: In typography, the curved part of the character that encloses the circular or curved parts (counter) of some letters such as d, b, o, D, and B is the bowl. Some sources call any parts of a letter enclosing a space a bowl, including both parts of a double-storey g and the straight stem on a D or B. The curved strokes of a C are sometimes also referred to as bowls although they aren’t closed.
The shape and size of the counter and bowl can affect readability and is also an identifying factor for some typefaces.
At small sizes or at low resolution the bowls of some letters may fill in and appear solid. Print at a larger size, higher resolution, or change to a different typeface if this becomes an issue. Heavy typefaces or ones with normally small bowls and counters are especially prone to closing up.