LINK / CITE ADD TO WORD LIST. adjective. The definition of precious is something of great value or that is greatly loved. 1  An example of precious is priceless jewelry.
However, we can always point to the latest version under a particular category. The Current supported official version, which is the generally distributed and widely available latest version of Firefox, is Firefox 38.0.5. This version had an official release on June 2nd, 2015.
Nightly introduces Firefox 43.0a1. You can see what's planned for this version by visiting the Fixtures/Release Tracking page, although note that most of these features are not implemented in Nightly. One interesting point to note is that Nightly also offers a 64-bit version of Nightly for Windows as well as Linux.