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

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

The bank expects resilient demand and cash flow across the sector, supported by stimulus safeguarding local supply chains and acceleration of import substitution, to partially offset prolonged volatility risks.

From The Wall Street Journal • Mar. 25, 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

With the substitution exposed, Fox claimed the error was inadvertent.

From Salon • Mar. 9, 2026

The “unbreakable” Pletts Cryptograph relied in part on keyword ciphers, a type of substitution cipher.

From "The Woman All Spies Fear" by Amy Butler Greenfield