nonsuccessful

Nonsuccessful is an adjective used to describe something that fails to achieve its intended result, objective, or predefined criteria. It characterizes outcomes, processes, or attempts that do not attain the desired level of success. In formal writing, nonsuccessful is often preferred where a precise distinction from mere failure is desired, though it is less common in everyday language where unsuccessful is more frequent.

It can apply across domains, including science, business, policy, and project management. A nonsuccessful experiment may fail to produce a statistically significant effect or to meet endpoints. A nonsuccessful marketing campaign would not meet its ROI or engagement targets. In evaluating programs, researchers or managers may label certain outcomes as nonsuccessful to indicate a lack of attainment without judging the broader effort as a total failure.

Formation and usage: The word is formed from non- + successful. Some style guides prefer non-successful or hyphenated forms; others use nonsuccessful without a hyphen. In many contexts, the more common opposite is unsuccessful, which can carry a similar meaning with a broader, everyday register. The noun form nonsuccess is rare, and nonsuccessful as a noun is generally avoided.

Related terms include unsuccessful, failure, negative outcome, and null result.