The original
Cyrillic alphabet had 43
letters, which were necessary for the
Old Church Slavonic language of
Cyril and Methodius; modern
Russian uses only 33 of them.
Bulgarian,
Serbian, and other
Slavic languages use even fewer.
A lesser-known fact about the Cyrillic alphabet is that while most of its characters derive from Greek, three come from Hebrew. The characters for sh, shch, and ts are square, boxy versions of the Hebrew letters shin and tzaddi.