The word is front, as in a weather front, cold front, warm front, etc.
A boundary between 2 air masses of different density moisture or temperature is a front.
boundary
boundary
Never cross the boundary. Boundaries are important for schools. This is the boundary between the U.S. and Canada.
That fence is the boundary between our property and our neighbor's property. Their favorite ski hill is located on the boundary between the two cities.
A boundary is a restriction, a line of demarkation. That fence is the boundary between our property. The ball went outside of the boundary.
The cell membrane is a organelles that is boundary between a cell and its environment.
border, frontier, edge, limit, perimeterif you mean that word is BOUNDARY......... this is its synonym: border, frontier, borderline
Border, boundary, edge, limit.
The boundary can usually be called the water's edge, or when one is talking about a beach, the word 'shore' is used.
The word could be border, boundary, edge, periphery, or purlieu.
Rift valley