Definition:Subinterval
Definition
Let $I$ be a real interval.
A subinterval $J$ of $I$ is a real interval such that $J \subseteq I$.
A purely intuitive definition which may or may not be accurate -- for example, is $\left({a \,.\,.\, b}\right)$ strictly speaking a subinterval of $\left[{a \,.\,.\, b}\right]$?
If you are fairly certain that all issues are dealt with, please remove {{proofread}} from the code.
