Re: Simple enough for every reader?

On 10.07.2025 11:47, Mikko wrote:

On 2025-07-09 16:35:02 +0000, WM said:
 

On 09.07.2025 10:34, Mikko wrote:

On 2025-07-08 15:47:12 +0000, WM said:
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On 08.07.2025 09:46, Mikko wrote:

On 2025-07-07 15:37:08 +0000, WM said:
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On 07.07.2025 10:29, Mikko wrote:
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Bijection requires completeness of domain and codomain.

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So you say but cannot prove.

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It is so by definition. See e.g. W. Mückenheim: "Mathematik für die ersten Semester", 4th ed., De Gruyter, Berlin (2015).

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Can you refer to some better author?

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That is hardly feasible. But you can look up the definition in every textbook of your choice. You will find the same result. Even Wikipedia will be sufficient: a bijection is a relation between two sets such that each element of either set is paired with exactly one element of the other set.

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So no requirement of completeness.

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"Each element" means that none is missing.

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No, it does not. What is said about each element applies to missing
elements, too.
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In mathematics, a surjective function (also known as surjection, or onto function is a function f such that, for every element y of the function's codomain, ... [Wiki]

 That text does not say that

There is none missing.

Try to learn to understand mathematical texts. Every means none is missing, formally abbreviated by the universal quantifier ∀. Until you got it: EOD.
Regards, WM