It sounds like you might have a crack in your radiator or reservoir and will need to get it repaired or replaced.
The reservoir is always either full or empty.
If you are talking about a vehicle, then the coolant level is critical for generating heat. Check you vehicle coolant reservoir if it is empty, wait until the engine is cool and check the level of coolant in the radiator and fill as recommended with the appropriate kind of coolant then fill the reservoir to the level indicated.
What I use on my engine coolant reservoir is a cheap plastic turkey baster from Wallmart ( it didn't take as long as I thought ) You should be able to empty the windshield washer fluid reservoir the same way
The windshield washer reservoir is almost empty!
gross weight of a vehicle is the weight of the vehicle and all load, not an empty weigh
Your radiator appears empty because your cooling system has a leak.
"the horseshoe" sounds like a reservoir icon; check your fluid levels. Suspect wiper reservoir empty.
If the clutch fluid reservoir is just low, no. If the clutch fluid reservoir is empty, yes.
Could be a bad water pump or a leak in the line
Water is used to cool things down.
Find and repair the leak. Refill the reservoir and pray that you didn't burn out the pump. Check for air bubbles or foam.
No, only if both sets are empty. The intersection of disjoint sets is always empty.