Substitution

In general, substitution is the replacement of one thing with another. There are many specific examples:

• In organic chemistry, a reaction where one functional group takes the place of another. A major type of substitution is nucleophilic substitution.

• The substitution cipher in cryptography.

• The substitution rule in calculus.

• Import substitution in trade.

• The substitution method in the testing of optical fiber.

• The substitution property of equality in mathematics.

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