Definition:Real Interval/Unit Interval/Closed

Definition
The closed interval from $0$ to $1$ is denoted $\mathbb I$ (or a variant) by some authors:
 * $\mathbb I := \left [{0 \,.\,.\, 1} \right] = \left\{{x \in \R: 0 \le x \le 1}\right\}$

This is often referred to as the closed unit interval.

Also denoted as
Sources which use the $\textbf{boldface}$ font for the number sets $\N, \Z, \Q, \R, \C$ tend also to use $\mathbf I$ for this entity.

Some sources merely use the ordinary italic font $I$.