In chemistry, water is actually an acid and a base, albeit weak ones.   Water is both a weak acid and base because its ionization constant is
10^-7.  This is how water can create something like the Grand canyon via erosion?  We usually consider waster to be neutral, however, in terms of classifying water from a chemical analysis standpoint, water has the properties of an acid and a base.  The following are various definitions of the acid/base dichotomy:

Arrhenius:
acid: generates [H+] in solution
base: generates [OH-] in solution

Brønsted-Lowery:
acid: anything that donates a [H+] (proton donor)
base: anything that accepts a [H+] (proton acceptor)

Lewis:
acid: accepts an electron pair
base: donates an electron pair

THC Loadee