According to the PMBOK® Guide and the PMI Lexicon of Project Management Terms, the definition of risk is centered on the concept of " uncertainty. "

Definition of Individual Project Risk: An uncertain event or condition that, if it occurs, has a positive or negative effect on one or more project objectives (such as scope, schedule, cost, and quality).

The " Effect of Uncertainty " : This specific phrasing— " the effect of uncertainty " —is the standard definition used by both PMI and ISO 31000. It acknowledges that risk is not just about the event itself, but how the lack of certainty regarding that event influences the ability of the organization to reach its goals.

Positive vs. Negative: Organizations view risk as a " double-edged sword. " While many people equate risk only with threats (negative), professional project management recognizes opportunities (positive risks) as well. Therefore, defining it simply as a " negative impact " (as in options C and D) is incomplete.

Organizational Risk Appetite: How an organization perceives these uncertainties depends on its Risk Appetite (the degree of uncertainty it is willing to take on) and Risk Threshold (the level of impact at which a stakeholder may have a specific interest).

Comparison with other options:

A. events that will inevitably impact...: Risk is by definition uncertain. If an event is " inevitable " (100% probability), it is no longer a risk; it is a fact or an issue that must be managed as a known constraint.

C. events which could have a negative impact...: This describes Threats. While correct in a narrow sense, it ignores the " Opportunities " side of risk management (positive risks).

D. the negative impact of undesired events...: Similar to option C, this focuses exclusively on the negative aspect. Professional project management seeks to maximize opportunities just as much as it seeks to minimize threats.