Display style in text, but at text style size

Question

I would like to write $\sum_i$ to be displayed as \displaystyle $\sum_i$ but at the size of $\sum_i$. How can I do that?

I could maybe use a subscript command, but that is not my question. My question is more generic about the display style within the text style at the size of the text style.

Answer 1

Use \limits.

\documentclass{article}
\usepackage{mathtools}
\begin{document}
abc $\sum_i$ $\sum\limits_i$ def
\end{document}