Remove section numbers latex - latex

Question

I have a problem with section numbering in latex. I want to remove the section numbers from headings and contents but I want the numbers to be there for lemmas, theorems etc. I want it to look like:
Section Whatever
Some unimportant text.
Section Whatever else
Another unimportant text.
Lemma 2.1
Theorem 2.2
Section Whatever again
Theorem 3.1
How can I do it? I tried
\renewcommand\thesection{}
but it removes the numbers even from lemmas and theorems. Thank you very much :)

Answer 1

Under the default article class we can merely remove the formatting applied to the section counter by adding
\makeatletter
\renewcommand{\#seccntformat}[1]{}
\makeatother
to the preamble. This will remove all sectional title numbering (\sections, \subsections, \subsubsections, ...), yet keep them where they are references or whenever \thesection is used.
\documentclass{article}
\newtheorem{theorem}{Theorem}[section]% Theorems numbered by section
\newtheorem{lemma}[theorem]{Lemma}% Lemma uses theorem's counter
\makeatletter
\renewcommand{\#seccntformat}[1]{}
\makeatother
\begin{document}
\section{Section whatever}
Some uninportant text.
\section{Section whatever else}
Another uninportant text.
\begin{lemma}
Some lemma.
\end{lemma}
\begin{theorem}
Some theorem.
\end{theorem}
\section{Section whatever again}
\begin{theorem}
Another theorem.
\end{theorem}
\end{document}