preposition / adverb / adjective
under
UN-dur/ˈʌndər/
Below a specified position or level.
A red ball rests directly under a wooden table.

Etymology
Old English under already expressed a position beneath something else. The selected meaning preserves that concrete spatial relationship: something above supplies the reference point for what lies below.
In context
The deck shifts a little under you. You widen your stance to keep your balance.
More examples
- She slides the tray under the shelf.
- The swimmer takes a breath before diving under.
- Keep the temperature under 40 degrees.
Similar words
- below
- Often describes a lower level without being directly underneath.
- underneath
- Emphasizes being directly below something, often covered or hidden.