\documentclass[12pt,a4paper]{article}
\usepackage[greek,english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{alphabeta}
\usepackage{amsmath}
\usepackage{multirow}
\begin{document}
\section{Πίνακας}
\begin{table}[h]
	\centering
	\begin{tabular}{|c|l|r|c|c|}
	\hline
	\multirow{2}{*}{Κατάσταση} & \multicolumn{4}{c|}{PT} \\ \cline{2-5}
				    & $S_1$ & $S_2$ & $S_3$ & $S_4$ \\ \hline
	\multirow{2}{*}{MR1}       & 0.1 & \multirow{2}{*}{0.7} & 0.2 & 0.3 \\ \cline{2-2} \cline{5-5}
				    & 0.1 &                       &     & 0.2 \\
	\hline
	\end{tabular}
	\caption{my caption} \label{tbl:1}
\end{table}
\end{document}
