A pH level of 9 is considered to be basic or alkaline. The pH scale is a measure of the acidity or basicity of a solution, with a pH value of 7 being neutral, values below 7 being acidic, and values above 7 being basic. A pH of 9 indicates a relatively high concentration of hydroxide ions (OH-) in the solution compared to hydrogen ions (H+), resulting in an alkaline nature.