A working hypothesis is

Concept. In research methodology a hypothesis is a tentative, testable proposition about a relationship between variables, advanced before the evidence has settled the matter. A working hypothesis is the provisional form of such a proposition: it is adopted at the outset of an enquiry as a starting assumption that gives the investigation its direction, and it is held only so long as the accumulating evidence permits. Its two defining marks are therefore that it is tentative, meaning not yet established, and instrumental, meaning it exists in order to guide and to be tested by further enquiry.

Application. The stem asks what a working hypothesis is, so the description must satisfy both marks at once. The tentative mark requires wording that grants the proposition only conditional standing rather than settled truth; the instrumental mark requires that the proposition be adopted for the sake of enquiry still to come. A hypothesis that is provisionally accepted for further research satisfies both: provisional acceptance is exactly conditional standing, and acceptance for further research is exactly the forward-looking, investigation-guiding role.

Cross-check. Place the alternatives along the same verification sequence and the distinction becomes explicit:

• A hypothesis already proven: once verification has succeeded the proposition is no longer tentative and is reported as a finding or an established conclusion, so it cannot serve as the starting assumption of an enquiry that has yet to be carried out.

• A proposition not required to be tested: testability is the entry criterion for a hypothesis, so a statement granted without empirical examination belongs to the class of assumptions, postulates and axioms.

• A scientific theory: a broad, well-substantiated explanatory framework that accounts for a large body of evidence and itself generates further testable predictions. It is a system of explanation, not the single provisional proposition with which a particular enquiry begins.

A working hypothesis is therefore a provisionally accepted hypothesis for further research: tentative in standing and instrumental in purpose.