The countdown and launch of a rocket, missile or spacecraft
The start of the landing area of a runway.
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 point where one mentally or physically is vulnerable in response to provocation or to particular things in general. As in emotions, stress, or pain.
An entrance; the door or gate of a house.
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.