Assumption

Assumption is a factor in the planning process considered to be true, real, or certain, without proof or demonstration.

Definition

According to the PMI Lexicon of Project Management Terms,

Assumption. A factor in the planning process considered to be true, real, or certain, without proof or demonstration.

According to the BABOK Guide (3rd edition),

Assumption. An influencing factor that is believed to be true but has not been confirmed to be accurate, or that could be true now but may not be in the future.