Definition:Assumption

Definition
An assumption is a statement which is introduced into an argument, whose truth value is (temporarily) accepted as True.

In mathematics, the keyword let is often the indicator here that an assumption is going to be introduced.

For example:
 * Let $$p$$ (be true) ...

can be interpreted, in natural language, as:
 * Let us assume, for the sake of argument, that $$p$$ is true ...

Also see

 * An axiom, which is accepted as being unconditionally true.


 * A premise, which is a statement which is specifically used for the purpose of deriving a conclusion.
 * An assumption may be used as a premise at any stage of an argument.
 * The conclusion of one argument may also be used as a premise in another argument.