The most advanced or recent version of something; leading edge.
The part of a country which borders or faces another country or unsettled region.
To live as pioneers on frontier territory.
Any end or boundary.
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.
An entrance; the door or gate of a house.
The quantitative point at which an action is triggered, especially a lower limit.
The wage or salary at which income tax becomes due.