Interval
A collection of points on a Line Segment. If the endpoints 
and 
are Finite and are included, theinterval is called Closed and is denoted 
. If one of the endpoints is 
,then the interval still contains all of its Limit Points, so 
and 
arealso closed intervals. If the endpoints are not included, the interval is called Open anddenoted 
. If one endpoint is included but not the other, the interval is denoted 
or 
and iscalled a Half-Closed (or Half-Open) interval.
- Ulam's Problem
- Ultrametric
- Ultraradical
- Ultraspherical Differential Equation
- Ultraspherical Function
- Ultraspherical Polynomial
- Umbilic Point
- Umbral Calculus
- Umbrella
- Unambiguous
- Unbiased
- Uncia
- Uncorrelated
- Uncountable Set
- Uncountably Infinite Set
- Undecagon
- Undecidable
- Undecillion
- Undetermined Coefficients Method
- Undulating Number
- Unduloid
- Unexpected Hanging Paradox
- Unfinished Game
- Unhappy Number
- Unicursal Circuit