pH

1 of 2

noun

ˈpē-ˈāch 

: a measure of acidity and alkalinity of a solution that is a number on a scale on which a value of 7 represents neutrality and lower numbers indicate increasing acidity and higher numbers increasing alkalinity and on which each unit of change represents a tenfold change in acidity or alkalinity and that is the negative logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity in gram equivalents per liter of the solution

also : the condition represented by a pH number

PH

2 of 2

abbreviation

1

pinch hit

2

public health

3

Purple Heart

Examples of pH in a Sentence

Recent Examples on the Web

Noun

To make their product, the food company’s scientists collect living cells from Pacific salmon and grow them in cell cultivators that mimic the inside of a wild fish—controlling factors like temperature, pH and nutrients, per their website. —Margherita Bassi, Smithsonian Magazine, 11 June 2025

How to Test Your Garden Soil’s pH Level in 4 Simple Steps 4. —Rita Pelczar, Better Homes & Gardens, 28 May 2025

Understanding Soil pH Soil pH affects how well plants take up nutrients. —Lauren Landers, Better Homes & Gardens, 9 Apr. 2025

Acidity is measured by pH, which ranges from 0 as the most acidic to 14 as the most alkaline. —Nancy Lebrun, Verywell Health, 26 Nov. 2024

Word History

Etymology

Noun

German, from Potenz power + H (symbol for hydrogen)

First Known Use

Noun

1909, in the meaning defined above

Phrases Containing pH

• pH meter

Kids Definition

pH

noun

(ˈ)pē-ˈāch 

: a number used in expressing acidity or alkalinity on a scale whose values run from 0 to 14 with 7 representing neutrality, numbers less than 7 increasing acidity, and numbers greater than 7 increasing alkalinity

also : the condition represented by such a number

Medical Definition

ph

1 of 2 abbreviation

1

pharmacopoeia

2

phosphor

3

phot

pH

2 of 2 noun

(ˈ)pē-ˈāch 

: a measure of acidity and alkalinity of a solution that is a number on a scale on which a value of 7 represents neutrality and lower numbers indicate increasing acidity and higher numbers increasing alkalinity and on which each unit of change represents a tenfold change in acidity or alkalinity and that is the negative logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity in gram equivalents per liter of the solution

instead of saying that the concentration of hydrogen ion in pure water is 1.00 x 10⁻⁷, it is customary to say that the pH of pure water is 7

—Linus Pauling

also : the condition represented by such a number compare pk