The chemical formula for pure water is H2O. Pure water breaks up into an equal number of H+(aq) and OH-(aq) ions. As the amounts of the H+ and OH- ions are equal, water is said to be neutral.
However, solutions with more H+ ions than OH- ions (for example, HCl) are said to be acidic. Solutions with more OH- ions than H+ ions (for example, NaOH) are said to be alkaline (or basic).