I'm sorry for my English.
I just need to make a table with some long sentences. When I'm doing it I get the following result (see the picture), using the following code:
\begin{center}
\begin{tabular}{|c|c|c|c|c|}
\hline
Система & Кинетическая энергия $T$ & Потенциальная энергия $U$ & \multicolumn{2}{|c|}{Степени однородности} \\ \cline{4-5}
& & & $h_T$ & $h_U$ \\ \hline
Одномерный гармонический осциллятор & $\sim (\dot{x})^2$ & $\sim -x^2$ & 2 & 2
\end{tabular}
\end{center}



\begin{center}...\end{center}-- users have to build the\documentclass{...}...\begin{document}...\end{document}code around your fragment, this is extremely tedious. The harder this is, the fewer help you will get. And perhaps this is the reason why someone (no, not me!) downvoted your question. – Jul 31 '15 at 22:47