ELI5: Explain Like I'm 5

Well-quasi-ordering

Okay, little one, let me explain what a "well-quasi-ordering" is.

Imagine you have lots of different shapes and you want to organize them. You could put the squares first, then the circles, then the triangles, and so on. This is called ordering. But what if you have shapes that can't be compared, like a square and a circle? That's where a well-quasi-ordering comes in.

A well-quasi-ordering is a way to organize things that can't be directly compared. You look for similarities and differences between the things you want to organize, and then you create groups based on those similarities and differences. Then, within each group, you order the things in a way that makes sense.

For example, you could group all the shapes with straight sides together and all the shapes with curved sides together. Within each group, you could then order them by how many sides they have, with the shapes with fewer sides coming first.

A well-quasi-ordering is useful in lots of different situations. For example, you could use it to organize words in a language based on their similarities and differences, or to organize different species of animals based on their physical characteristics.

Basically, a well-quasi-ordering is a way to organize things that can't be directly compared by finding similarities and differences and grouping them in a way that makes sense.
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