# Definition:Limit of Real Function/Intuition

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## Definition

Though the founders of Calculus viewed the limit:

- $\ds \lim_{x \mathop \to c} \map f x$

as the behavior of $f$ as it gets infinitely close to $x = c$, the real number system as defined in modern mathematics does not allow for the existence of infinitely small distances.

But:

- $\exists L: \forall \epsilon \in \R_{>0}: \exists \delta \in \R_{>0}: 0 < \size {x - c} < \delta \implies \size {\map f x - L} < \epsilon$

can be interpreted this way:

*You want to get very close to the value $c$ on the $\map f x$ axis.*

*This degree of closeness is the positive real number $\epsilon$.*

*If the limit exists, I can guarantee you that I can give you a value on the $x$ axis that will satisfy your request.*

*This value on the $x$ axis is the positive real number $\delta$.*

## Sources

- For a video presentation of the contents of this page, visit the Khan Academy.