Usability is an approach to product development that incorporates direct user feedback throughout the development cycle in order to reduce costs and create products and tools that meet user needs. There are many definitions of usability from books by usability professionals.

"[Usability refers to] the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use." - ISO 9241-11

The business benefits of adding usability to a product development process include:

- Increased productivity
- Increased sales and revenues
- Decreased training and support costs
- Reduced development time and costs
- Reduced maintenance costs
- Increased customer satisfaction

Too often, organizations don't track total lifecycle costs for a project. The original development budget and schedule is known, but they don't typically track how expensive support costs are, what they're attributable to, how much employee time is wasted on unusable tools, and other post-production factors. Thus, projects that have small up-front costs and short development cycles are often rewarded even if they result in failed, ineffective, or unusable products. There are many real world examples showing how usability can benefit a project - or its lack hurt.

The average software program has 40 design flaws that impair employees' ability to use it. The resulting cost of lost productivity can be up to 720%. (Landauer, 1995, The Trouble With Computers , MIT Press.)