The Rotokas alphabet of Bougainville Island has fewer letters than any other alphabet in modern use.
More than four thousand people speak Rotokas, and it sounds something like this:
Vo tuariri rovoaia Pauto vuvuiua ora rasito pura-rovoreva. Vo osia rasito raga toureva, uva viapau oavu avuvai. Oire Pauto urauraaro tuepaepa aue ivaraia uukovi.
(That’s the start of Genesis, by the way; “Pauto” is the Rotokas word for God.)
You may have noticed that there aren’t too many letters in that excerpt: A, E, I, O, U, G, K, P, R, S, T, and V. But that’s all the letters in Rotokas. Twelve: that’s it. Central Rotokas (one of three dialects of Rotokas) has an exceptionally small phonemic inventory, and an alphabet to match.
A phonemic inventory, by the way, is the whole set of meaningful sounds in a language. English has quite a few different vowels (up to 21 in some dialects) but an average number of consonants (around 24). On the other end of the scale from Rotokas are the !Kung languages, which may have as many as 141 distinct meaningful sounds.