- universal time
- universal time system
- universal transverse Mercator projection
- universal Turing machine
- universal unfolding
- universal vector bundle
- universal volume formula
- universe of Boolean-valued sets
- universe of constructible sets
- universe of discourse
- universe or cosmos
- UNIX operation system
- UNIX操作系统
- unknotted knot
- unknown number
- unlimited covering surface
- unlimited register machine
- unordered pair
- unordered pair
- unordered pair
- unoriented cobordism class
- unramified extension
- unramified extension
- unramified morphism
- unrectifiable curve