Let $[a, b] \subset \mathbb{R}$ be a D544: Closed real interval such that

(i)	\begin{equation} a < b \end{equation}
(ii)	$f : [a, b] \to \mathbb{R}$ is a D4364: Real function on $[a, b]$

Then $f$ is a Riemann integrable real function on $[a, b]$ if and only if \begin{equation} \exists \, R \in \mathbb{R} : \forall \, \varepsilon > 0 : \exists \, \delta > 0 \left( P \text{ is a tagged partition for } [a, b] \text{ with } \text{Mesh}(P) < \delta \quad \implies \quad \left| \mathcal{R}_P(f) - R \right| < \varepsilon \right) \end{equation}