substitution

British  

/ ˌsʌbstɪˈtjuːʃən /

noun

1. the act of substituting or state of being substituted

2. something or someone substituted

3. maths the replacement of a term of an equation by another that is known to have the same value in order to simplify the equation

4. maths logic

   1. the uniform replacement of one expression by another

   2. an expression so derived from another

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Explanation

The noun substitution refers to the act of replacing one thing with another. Your football coach might make a substitution by sending you onto the field to take over for a player who is tired or injured. Substitution comes from the Middle French word of the same spelling, meaning "a putting in place of another." You might notice that substitution contains the root word substitute, and that's a good way to remember the meaning of the word. In school, a substitute is a temporary teacher who fills in when your regular teacher is out — in other words, a substitution has been made until your teacher returns.

Example Sentences

Those people are spending money they likely would have spent in the city anyway, a principle economists call substitution.

From Salon • Apr. 30, 2026

The Waitress, a last-minute substitution at the banquet, is the mother of one of the dead.

From The Wall Street Journal • Apr. 8, 2026

Recessions are generally characterized, in the first instance, by the substitution of a sudden, sharp, upward movement in the unemployment rate for a gradual downward or sideways movement.

From Barron's • Apr. 3, 2026

It also can measure the limits of releases from strategic petroleum reserves, spare production capacity, freight constraints and refinery substitution, he said.

From MarketWatch • Mar. 24, 2026

For their secret language, they had decided on a substitution cipher.

From "Book Scavenger" by Jennifer Chambliss Bertman