pH

noun · Chemistry

Definition

A scale, usually from 0 to 14, that measures how acidic or alkaline a solution is.

Explanation

Below 7 is acidic, 7 is neutral and above 7 is alkaline. Each unit is a tenfold change in hydrogen ion concentration.

Example

Lemon juice has a low pH.

Common confusion

A difference of one pH unit is a factor of ten, not a small step.