When most people say “Arduino” they mean an ATmega328 based board like the Uno.  This means a simple 8-bit microcontroller with only 2K of RAM.  That’s 2,048 bytes of memory to work with.  So when someone asked me if the Arduino could do speech recognition, to be honest, I laughed.  Then my jaw dropped when I saw µSpeech.  A speech recognition library for the Arduino Uno’s ATmega328.