The category in Factorio that includes "water" and "oil" is best called Fluid, not "liquid". The words "liquid" and "gas" specifically describe types of matter: solid or liquid or gas (or plasma; see Wikipedia). "Fluid" is often used to mean "liquid", but technically is not the same type. It is anything that flows, and can be either a liquid or a gas.
I would rename the page, but there are a lot of subpages and language pages that use Liquid. I don't want to break everything.
The description of boilers and steam engines also use "fluid" so that's what we should use. I think "system" is unnecessary too. Will things break if you use the redirect option? metarmask (talk) 14:50, 3 February 2017 (UTC)