The order of terms matters even when they commute

When writing a term that consists of several factors, the conventions regarding their order appear arbitrary. It is usual to write:

• $xy$ and $yx$ in either order;
• $5t$ but not $t5$ (to avoid confusion with $t_5$ or $t^5$);
• $x\sqrt{2}$ but not $\sqrt{2}x$ (to avoid confusion with $\sqrt{2x}$).
• $\sqrt{2}\sin x$ but not $\sin x \sqrt{2}$ (to avoid confusion with $\sin \left(\sqrt{2}x\right)$).