# Definition:Strictly Negative Real Function

## Definition

Let $I$ be a real interval.

Let $f$ be a real function.

Then $f$ is strictly negative (on $I$) if and only if:

$\forall x \in I: \map f x < 0$

## Also known as

A strictly negative real function is also described as a negative real function, but this causes confusion with a non-positive real function and so this usage is to be avoided.