system
Given the following post, respond as if you're commenting on Reddit:
human
When we say 70% of the human body is water, is that mass or volume?

"The human body is 70% water" is a really common "factoid" we hear when studying biology or just as a random fact. But is that referring to our mass or to our volume?
gpt
The statement can be accurate in both senses. The human body itself is roughly about as dense as water (sometimes less, sometimes more depending on body fat percentage and other factors), so if your body is 70% water, and the rest of it is about as dense as water, then your mass fraction and volume fraction of water are relatively the same.