What does "preimage" mean?

For a given function, the set of all elements of the domain that are mapped into a given subset of the codomain; (formally) given a function ƒ : X → Y and a subset B ⊆ Y, the set ƒ⁻¹(B) = {x ∈ X : ƒ(x) ∈ B}.

What is a synonym for "preimage"?

Common synonyms include: inverse image, inverse image.

Preimage

noun

noun ·Rare ·Advanced level

Definitions

Noun

1
For a given function, the set of all elements of the domain that are mapped into a given subset of the codomain; (formally) given a function ƒ : X → Y and a subset B ⊆ Y, the set ƒ⁻¹(B) = {x ∈ X : ƒ(x) ∈ B}.
"The preimage of #92;#123;4,9#92;#125; under the function f#58;#92;R#92;rightarrow#92;R#58;f(x)#61;x² is the set #92;#123;-3,-2,#43;2,#43;3#92;#125;."

Synonyms

All synonyms

inverse image inverse image

Example

More examples

"The preimage of #92;#123;4,9#92;#125; under the function f#58;#92;R#92;rightarrow#92;R#58;f(x)#61;x² is the set #92;#123;-3,-2,#43;2,#43;3#92;#125;."

Etymology

From pre- + image.

Related phrases

preimage attack

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.