olemus
maht: kontekstist sõltuv suuruse mõõt
ruumala: kolmemõõtmelise ruumiosa suuruse mõõt

Wiktionary:
1. a three-dimensional measure of space that comprises a length, a width and a height
It is measured in units of cubic centimeters in metric, cubic inches or cubic feet in English measurement.
The room is 9x12x8, so its volume is 864 cubic feet.
The proper products can improve your hair's volume.
https://en.wikipedia.org/wiki/Volume

Wiktionary:
8. Quantity
The volume of ticket sales decreased this week.

vt ka
- andmemaht
- maht (1)
- mahtküünaldiagramm
- mahtrünne