\begin{definition}[Definition:Assumption]
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''' ...
\end{definition}