What is an uncertain event or condition that has a positive or negative effect on a project’s objectives?

The PMBOK® Guide defines risk as "an uncertain event or condition that, if it occurs, has a positive or negative effect on a project’s objectives". A workaround is applied in response to an unidentified negative risk that has occurred. An issue can be described as a negative risk or currently occurring event. A trigger (or risk trigger), is an event that signifies a risk is going to materialize.