UK mortgage terminology

This article gives descriptions of mortgage terminology in the United Kingdom which can often be unclear to borrowers.
Introduction.
The UK mortgage market is one of the most innovative and competitive in the world. Most borrowing is funded by either mutual organisations (building societies and credit unions) or proprietary lenders (typically banks). For a number of years the market operated with minimal state intervention, although this changed at least temporarily following the 2008 nationalisation of Northern Rock, which at the time was one of the country's largest mortgage banks.
Since 1982, when the market was substantially deregulated, there has been substantial innovation and diversification of strategies employed by lenders to attract borrowers. This has led to a wide range of mortgage types.