How is "Turnover" in HKEX different from "Volume"?

External question — Personal Finance Stack Exchange Author: Raven Cheuk Original post: https://money.stackexchange.com/questions/137332 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. On page 26 of this PDF provided by HKEX, it describes turnover as: each trade concluded in the derivatives market will increase the turnover for that day Isn't it the definition for volume? When checking other documents from the HKEX websites, it seems their turnover is in the unit of HK dollar, which is a completely different concept of the turnover ratio in the US market. Then what is the meaning of "turnover" in HKEX?