# What is the opposite of epsilon

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## Main Question or Discussion Point

Is there a notation for the opposite of epsilon (infinitesimal) in the way that infinity is the opposite of zero?

jedishrfu
Mentor
I don't think there is a definitive term, I've seen people use these terms:
- immeasureable
- infinite

Ssnow
Gold Member
For every $\varepsilon >0$ ''very small'' you have $\varepsilon^{-1}=\frac{1}{\varepsilon}$ is ''very big'', in general there is no a preferred symbol to denote this ...

Usually, people like to use capital letters for this, such as $H$ or $N$.

jedishrfu
Mentor
What does the H or N stand for?

fresh_42
Mentor
Perhaps $N$ for number such as $N(ε)$. I've also seen $C$ for a constant. But I've never seen a huge $H$.

"The nightmare of mathematician is a sequence $\varepsilon_n$ that tends to infinity, as $n \to 0$"
Paul Halmos

Is there a notation for the opposite of epsilon (infinitesimal) in the way that infinity is the opposite of zero?
The opposite of infinity is not zero, it's $\varepsilon$.
Source : This Numberphile video
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Depends how you define "opposite". If you mean additive inverse, then $-\infty$ would be the opposite of $\infty$, and $-\varepsilon$ for $\varepsilon$. If by "opposite" you mean multiplicative inverse, then the opposite of $\varepsilon$ would be $\infty$. Zero, on the other hand doesn't have a multiplicative inverse, so maybe we can say it doesn't have an opposite.