This question has been on my mind for a while. We so often see a recipe that calls for a small, medium, or large onion. But what does that mean? I didn't know, although I suspect that at least some here do. However, I believe that there are a lot of folks like me who couldn't say how big a described onion is.
This morning I decided to find the answer, and I found the Onion Sizing Guide:
https://owyheeproduce.com/wp-content/uploads/2022/07/Onion-Sizing-Guide.pdf
Maybe this will help those who, like me, are clueless about this.