Adaptive difficulty
Adaptive difficulty is a bitcoin protocol change proposal by Iain Stewart, with the goal of letting the typical time interval from one block to the next adjust smoothly to prevailing network latency, while not compromising the strength of the blockchain, or the decentralization of the network (in particular the ability of small miners to join in).
(uh, and now a pause folks, while I slowly learn everything I never wanted to know about how to type in mathematical notation to a wiki but have been forced to find out!)