What is the purpose of the suffix "さ" on adjectives like 美しさ and 多さ?
The former is the title of an essay by Banana Yoshimoto, so I don't have much context for it. The book editors translated it as "On beauty" which didn't help me understand what this さ business was all about.
In the case of the latter, she writes:
"品揃えの多さについつい買い込んでしまい、大荷物を抱えて併設の花屋に行った。"
Which I understand as:
"There were many goods there that, against my better judgement, I had purchased. Carrying the bags I went to the attached flower shop."