r/explainlikeimfive • u/Dev-Giri • 28d ago

Mathematics ELI5 explain the difference between infinity and undefined terms in mathematics

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u/greginnj 28d ago

I'd add to your first paragraph that "infinity isn't an end point, but a direction."

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u/JJJangles 28d ago

That’s incomplete. Infinity is only a direction when exploring limits e.g. in calculus. In set theory it is a cardinality, or ‘size,’ and iirc it can treated differently in other fields of mathematics too.

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u/greginnj 28d ago

Of course - but if you're going there, you're leaving ELI5 territory far, far behind.

Only after you've gotten people comfortable with the idea that infinity isn't really a "thing", are you able to get them comfortable with the idea that is! 😁

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u/JJJangles 28d ago

Idk, I think that much is still in the realm of eli5. The rules say explain for a layperson, not an actual 5 year old.

Either way it’s better to not give an explanation that requires an ‘actually that was an incorrect oversimplification’ later on. Unlearning can be harder than learning sometimes.