Entropy

Many people tend to think of entropy as the tendency of everything to descend into chaos.
What it is, however, has multiple definitions (see Wikipedia here for more). It's a scientific rather than a philosophical term, most easily understood as 'a measure of the partial loss of the ability of a system to perform work due to the effects of irreversibility' or 'an index of the tendency of a system towards spontaneous change'.

It suits the purposes of the story more as a description of the setting than of its ultimate end. Western civilisation has collapsed, leaving the rich hiding in their ivory towers whilst the remainder of the population scratch out what they can from the urban canyons.

Welcome to London, c. 2029...