What is a Window of Opportunity or Strategic Window? 

A window of opportunity, commonly referred to as a strategic window, is the period of time in which an approach or strategy can be employed to exploit (gain value from) a recognized opportunity (scenario where value can be acquired).  

The window of opportunity is highly relevant in competitive strategy and entrepreneurship. 

In competitive strategy, a firm undertakes activity with regard to its value offering or value proposition (such as differentiated, cost-saving, or niche-based focus). There may be a finite period of time during which specific actions will result in acquiring value at the expense of competitors. 

Similarly, in entrepreneurship, there may be a finite period of time during which a given course of action will result in the ability to extract value from the intended market for that value. It is closely related to the concept of Time to Market.