Modus tollens (lat. "the way that denies by denying") is a valid logical argument consisting of two premises and a conclusion, which altogether are constructed from two propositions $p$ and $q$ as follows:
Formally, modus tollens is the following logical argument: $$\begin{array}{rll} p\Rightarrow q&\text{major premise}&\text{e.g. If it is raining, then the roads are wet.}\\ \neg q&\text{minor premise}&\text{e.g. The roads are not wet.}\\ \hline \neg p&\text{conclusion}&\text{e.g. It is not raining.}\\ \end{array} $$
Proofs: 1