A financial call option allows the holder to buy a particular security at a particular price (the strike price) on or before a particular date but does not impose the obligation to do so. In other words, the purchaser of the option is betting that the option to buy will be valuable because the underlying security’s price will have gone up above the strike price. In many ways, Agile IT investments are like call options. The company invests money to build a subset of the features, which then gives it the option to continue investing and building more of the features—but it is not obliged to do so. If the additional features have become less valuable, for example, or if the initial features accomplish enough of the goal, then the company might decide not to make the incremental investment. That is powerful in an environment of uncertainty.
— War and Peace and IT: Glossary, Mark Schwartz