What is the name of a substance that can either donate a hydrogen ion or accept a
hydrogen ion depending on what it is reacting with (water is the most common
example)?
O acid
indicator
alkaline
O amphoteric

Water is amphoteric with both the acidic and basic characters.

Explanation:

As per the Bronsted Lowry theory of acids and bases,

Water has its own ability to either donate or accept hydrogen ions or protons.

If it accepts a proton then it is termed as basicTo accept a proton it should have a lone pair of  electrons.If it donates a proton then it is termed as acidicIf the water has the ability to accept as well as donating proton then it has both the acidic and basic characters and so it is termed as amphoteric in nature.  

It’s the energy source of stars