Which term refers to a factor believed to be true but not confirmed?

The term that refers to a factor believed to be true but not confirmed is "assumption." In the context of requirements analysis and design definition, an assumption is a condition that is taken for granted without verification. Assumptions are particularly important in the early stages of a project, where stakeholders may base their decisions and requirements on what they believe to be true, even if those beliefs haven't been validated.

Assumptions help to define the scope and direction of a project but can also introduce risks if they turn out to be incorrect. It is crucial for analysts to identify, document, and validate assumptions as part of their process to ensure that they do not lead to misunderstandings or project failures.

While a hypothesis is a proposed explanation that can be tested, speculation refers to conjecture that might not be grounded in any evidence, and a theory is generally a well-substantiated explanation based on a body of evidence. These terms carry different connotations and implications in the context of inquiry and knowledge validation, making "assumption" the most accurate choice for a factor believed to be true but not confirmed.