A Project Assumption is believed to be true either through Experience or high-level Historical Data.
A Project Assumption is stated without any empirical evidence.
All Project Assumptions are potential risks. Assumption Analysis is one of the important techniques for Risk Identification.
Project Assumptions should be well Documented and well Communicated. Poor Communication of Project Assumptions can, sometimes, lead to Project Failure.
Project Assumptions can be documented in any formal Document but preferably they should be documented in a separate Project Assumptions Log.
Bigger Project Assumptions must be Validated with other Stakeholders.