| Term | Definition |
|---|---|
| Underground |
Below ground level
|
| Underground parking |
Parking spaces or structures principally below ground level. Ventilation provisions are important compared to aboveground parking
|
| Underground planning |
Planning activity aiming to divide subsurface for human activities according to the ecological, economical and technical point of view
|
| Underground space |
Space created or used underground
|
| Underpass |
A structure, including its approaches which allows one road to pass under another road (or an obstacle)
|
| Unit |
Term sometimes used to refer to an element.
|
| User |
A person who uses a system for their own needs rather than one than operates it or observes its operation
|
