While the article goes into history and detail, here are a couple of analogies that may help explain what this thing is:<p>• The convention of specifying phone numbers using words, e.g. 1-800-FLOWERS (<a href="https://en.wikipedia.org/wiki/Phoneword" rel="nofollow">https://en.wikipedia.org/wiki/Phoneword</a>): this is the mapping<p><pre><code> 0 ↔ (space?)
1 ↔ ??
2 ↔ abc
3 ↔ def
…
9 ↔ wxyz
</code></pre>
Roughly, the Kaṭapayādi system is simply a different mapping between digits and letters.<p>• So a closer analogy may be, if the conventional English alphabet happened to list vowels (aeiouy, say) and consonants separately, then a mapping something like<p><pre><code> b c d f g h j k l m n p q r s t v w x z
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
</code></pre>
(so there are two choices for each digit, e.g. 2 can be represented by either 'c' or 'p'), with the decoding convention that we ignore vowels, and consonants that are immediately followed (in the same word) by another consonant. Then, to specify a sequence of digits like "314159265", we could write down below each digit the two possibilities for it:<p><pre><code> 3 1 4 1 5 9 2 6 5
d b f b g l c h g
q n r n s x p t s
</code></pre>
…and use these letters to make words. So something like "dine rob soul cottage" would stand for DNRBSLCTG = 314159265, as would "dumb funny sex parties" (= DBFNSXPTS = 314159265) or whatever. Then we could write rhyming poems or memorable prose, to memorize the digits (and transmit them accurately in an oral tradition).<p>With the English alphabet the above mapping would be hard to remember, but the alphabet in Sanskrit happens to be organized in a more orderly way, so it's easier to remember the mapping. (And the name helps: <i>ka</i> <i>ṭa</i> <i>pa</i> <i>ya</i> are simply the beginning (ādi) letters of each chunk mapping to 1234567890, the way our mapping above could be called the "B-N" mapping.)<p>Something close that there's a (recent) tradition of in English is "pilish": <a href="https://en.wikipedia.org/wiki/Pilish" rel="nofollow">https://en.wikipedia.org/wiki/Pilish</a> where the <i>lengths</i> of the words encode the digits, as in "how I wish I could remember pi" (=3141592). (See "Cadaeic Cadenza" and "Not a Wake": <a href="http://cadaeic.net/cadintro.htm" rel="nofollow">http://cadaeic.net/cadintro.htm</a> )