pH

The word “pH” means a scale from 0 to 14 measuring how acidic or alkaline a solution is, with 7 being neutral. In plain terms, a number showing how acidic or basic something is — low pH is acidic, high pH is alkaline, 7 is neutral.

Here is “pH” used in a sentence: “The gardener tested the soil's pH before planting the blueberries.”

“PH” is a noun.

The word “pH” dates back to around 1909. Introduced in 1909 by chemist S. P. L. Sørensen; the "H" stands for hydrogen, and the "p" likely abbreviates a word for "power" or "potential" in Sørensen's notation.

“PH” is a fairly common word in modern English, usually learned at around the B2 level.

By convention, pH is always written with a small "p" and a capital "H," even at the start of a sentence. The capital "H" refers to hydrogen, which is why it is not lowercased.

A low pH (below 7) means a solution is acidic, while a high pH (above 7) means it is alkaline, or basic. A pH of exactly 7 is neutral, like pure water.

pH is the scale used to measure how acidic or alkaline a solution is, whereas acidity refers to the acidic quality itself. A lower pH value indicates greater acidity.

The pH scale is usually described as running from 0 to 14, which covers the great majority of everyday solutions. Very strong acids or bases can technically fall slightly outside this range, but 0 to 14 is the standard reference.