Renaming Category to Product

I am using the Old Options theme with a child theme of light.
I do not think this is theme related. I would like to rename “Category”
To “Products” & would like to know how extensive this is. I would like to know if this could or has been done with a plugin. If this is a redundant question please forgive and direct me to the correct post. I have searched and not found an answer, I would think this to be and easy plugin.