A vestibule, foyer or entranceway with doors to the exterior on one end and doors to the interior on the other, functioning to keep indoor and outdoor air, humidity, and air temperatures separate.
A sealed, airtight chamber, such as in a manned spacecraft or submarine, used to provide access to and from the sealed area without allowing air out or water in.
An entrance; the door or gate of a house.
The outset of something; the point of entry, or the beginning of an action.
The bottom-most part of a doorway that one crosses to enter; a sill.
The start of the landing area of a runway.
The point where one mentally or physically is vulnerable in response to provocation or to particular things in general. As in emotions, stress, or pain.
The quantitative point at which an action is triggered, especially a lower limit.
Any end or boundary.
The wage or salary at which income tax becomes due.