A book containing references, alphabetically arranged, to the contents of a series or collection of documents or volumes; or a section (normally at the end) of a single volume or set of volumes containing such references to its contents.
Statistical indexes are also used to track or measure changes in the economy (for example, the Consumer Price Index) and movement in stock markets (for example, Standard & Poor's Index). Such indexes are usually keyed to a base year, month, or other period of comparison.
In mortgage financing, the term is used to determine adjustable-rate mortgage (ARM) interest rates after the discount period ends. Common indexes for ARMs are one-year Treasury Securities and the national average cost of funds to savings and loan associations.