Every discipline has its own vocabulary, and project management is no exception. This list of terms and definitions will help ensure that your PM communications are clear and understood by everyone. That way, when one person talks about risks, scope, issues, requirements and other project management concerns, everyone else knows what they’re referring to. This glossary contains common terms used in project management and can help start the standardization process in your organization.

From the glossary:

ASSUMPTION

External circumstances or events must occur for the project to be successful (or that should happen to increase your chances of success). If you believe that the probability of the event occurring is acceptable, you can list it as an assumption. An assumption has a probability between 0 and 100%; that is, it is not impossible that the event will occur (0%) and it is not a fact (100%) — it’s somewhere in between. Assumptions are important because they set the context in which the remainder of the project is defined. If an assumption doesn’t come through, the estimate and the rest of the project definition may no longer be valid.