The chart displays the segmental phonemes of twenty-five languages.
The languages included are:

     Arabic              Indonesian             Spanish (Spain)
     Chinese (Mandarin)  Italian                Swahili
     English             Japanese               Tagalog
     Finnish             Korean                 Tamil
     French              Persian                Thai
     German              Polish                 Turkish
     Hausa               Portuguese (Portugal)  Vietnamese (South)
     Hindi-Urdu          Russian                Yoruba
     Hungarian

The chart consists of several boxes, and each box corresponds to a
phoneme.  Thus, there are boxes for /a/, /b/, /d/, etc., many of which I
cannot display here since they use non-ascii IPA symbols.  Inside each
box is an array of 25 smaller boxes (5 by 5).  Each of these smaller
boxes corresponds to one of the 25 languages listed above.  If a smaller
box for a language is shaded, it indicates that the phoneme is present
in that language.

Thus, at a glance, the reader can determine whether a language has a
particular phoneme, as well as how many other languages have it.

For example, only five boxes are completely filled in: /t/, /k/, /s/,
/m/ and /u/, which indicates that all 25 languages have these phonemes.
Some phonemes are very common but not universal: only Japanese lacks
/l/; only Italian lacks /j/ (palatal semivowel); only Yoruba lacks /n/,
etc.  Some phonemes are quite rare: only Arabic, Hindi and Persian have
/q/ (unvoiced uvular stop); only Chinese, Hindi and English have /I/.
And so forth.

Anyway, now you'll know what I'm talking about when I refer to the
phoneme chart in the accompanying essay.