Apple has significantly updated Dictionary 2.0 for Mac OS X 10.5 Leopard, expanding it from a simple word lookup into a complete multilingual reference tool. Here's a look at what's new in Dictionary. Mac OS X is based on NeXTSTEP, the operating system Steve Jobs left Apple to develop back in 1986, and brought back in 1997. Nearly twenty years ago, NeXTSTEP included a "Digital Librarian" applicati