A more thorough explanation:

Definition: Supposition is the act of assuming something is true without any proof. It is a noun that means an assumption that something is true.

Example 1: She made the supposition that he was lying, but she had no evidence to support her claim.

Example 2: Without any supposition, the detective gathered evidence to solve the case.

The examples illustrate that supposition is an assumption made without any evidence or proof. In example 1, the person assumes that someone is lying without any evidence to support it. In example 2, the detective does not make any assumptions and instead gathers evidence to solve the case.