equation

noun

equa·​tion i-ˈkwā-zhən 

also -shən

1

a

: the act or process of equating

b(1)

: an element affecting a process : factor

(2)

: a complex of variable factors

c

: a state of being equated

specifically : a state of close association or identification

To bring governmental enterprises and payment for them into immediate equation …

—R. G. Tugwell

2

a

: a usually formal statement of the equality or equivalence of mathematical or logical expressions

b

: an expression representing a chemical reaction quantitatively by means of chemical symbols

Examples of equation in a Sentence

the equation of material wealth with happiness

Recent Examples on the Web

Rotation equation Starting pitcher Walker Buehler, who like France has more than six years of service time and can opt out today is he is not assured of being on the active roster, has made the team. —Kevin Acee, San Diego Union-Tribune, 21 Mar. 2026

Saturday, further uncertainty entered the equation, with guard Norman Powell listed as questionable due to calf tightness, having recently missed seven consecutive games due to a groin strain. —Ira Winderman, Sun Sentinel, 21 Mar. 2026

But these ghost particles do carry mass (and thus energy via Albert Einstein’s handy equation E = mc2). —Emma Gometz, Scientific American, 20 Mar. 2026

Even with Hendriks and Chafin out of the equation, there’s still spots to be locked in in the bullpen. —Betsy Helfand, Twin Cities, 20 Mar. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 1a

Phrases Containing equation

• characteristic equation
• cubic equation
• differential equation
• Diophantine equation
• enter (into) the equation
• equation of time
• linear equation
• parametric equation
• partial differential equation
• personal equation
• quadratic equation
• Schrödinger equation
• simple equation
• wave equation

Rhymes for equation

• abrasion
• caucasian
• eurasian
• evasion
• invasion
• occasion
• persuasion
• asian
• suasion
• athanasian

Kids Definition

equation

noun

equa·​tion i-ˈkwā-zhən 

also -shən

1

: the act or process of equating : the state of being equated

2

a

: a statement of the equality of two mathematical expressions

b

: an expression involving chemical symbols for a chemical reaction

Medical Definition

equation

noun

equa·​tion

i-ˈkwā-zhən also -shən

: an expression representing a chemical reaction quantitatively by means of chemical symbols