Definition: bouma is the shape formed by the outline of a word.
We recognize words from their word shape and psychologists call this image the Bouma shape based on the Dutch psychologist Herman Bouma who researched word-shape-based reading.

Lesson: The bouma of a word set in all caps is a rectangle. The bouma of a word set in lower case has a unique shape that needs to be considered when manipulating type, arranging elements, and laying out an ad.

Mind games: figure out these common words from their bouma shapes
Red = consonants, yellow = vowels

Two common phrases to decipher
In these mind games, the relative size of each letter is conveyed by its black box.

Answers to the above mind games.

Examples in practice

Business cards and letterheads often need bouma consideration. Many characters in the contact copy are already the height of upper case bands. Its an easy choice to simply set the copy in all caps. Readability is not affected since the words are few and the info has a captive audience - those seeking the information. (the above examples are for illustration purposes only - Jim's actual card has no mailing address and can be seen here.)

Here is a webpage in which improved consideration of the bouma of two words can enhance the layout:

Above: the bouma of the word Apps is within the U but does not respect the interior shape formed by the letter U.

Below left: the ascenders of the f and l in the word funnel capture some awkward space and the placement of the word forms a blank rectangle on the left.

Above right: A better layout - Setting the word APPS in upper case forms a straight-sided band that better respects the strokes of the letter U. Aligning the word funnel with the text copy below it increases the space on the right, improves the relationships among the text elements, and lets the layout 'breathe' more freely.

Side by side: Notice the improvements when the bouma of the words is thoughtfully considered.

Tip: See words as graphic elements to be manipulated - to enhance their clarity and comprehension.