There is an old and long followed adverb that says that “When opportunity knocks, you had better answer.” In that context, opportunity is viewed as a favorable situation that occurs that must be taken advantage of, however, opportunity can refer to any situation that may arise, and the chance to follow this path exists. Some opportunities can be negative in nature. Now, in the project management world, the term opportunity typically refers to the usage in a positive light. It refers specifically to a condition or situation that is favorable to the project, a set of circumstances that would be viewed as favorable to the project, a series of events or happenings that could be construed as favorable to the project, as well as any potential risks that could have a potentially positive impact on the sum total of all project objectives, as well as could potentially have a positive impact on any future changes that may take place. The direct contrast to the term opportunity could be the term threat.
This term is defined in the 3rd and the 4th edition of the PMBOK.