I have tried the code:
\begin{thebibliography}{0}
\bibitem{item1}
author 1 and author 2
\textit{The title}.
Thesis. SchoolName, 2018.
\end{thebibliography}
It outputs "References", but since I am using only one reference, I want to use "Reference"; that is, without the "s".
EDIT I used \documentclass{article}. What worked for me was using
\renewcommand\refname{Reference}
babelorpolyglossia. An answer that is guaranteed to work for you can only be found if we get to see a full minimal example document (a so-called https://tex.meta.stackexchange.com/q/228/35864) and not just code snippets. Anyway, https://tex.stackexchange.com/q/17445/35864 and https://tex.stackexchange.com/q/82993/35864 might already be enough for you. – moewe Aug 14 '19 at 06:21articledocument class,\renewcommand\refname{Reference}. In case of abookclass\renewcommand\bibname{Reference}. Otherwise, who knows ... – Fran Aug 14 '19 at 06:26