The imaginary line that separates river systems is called a "watershed" or "drainage divide." This line determines the direction in which water flows, with rivers on one side draining into one body of water and rivers on the other side draining into another. Watersheds can vary in size and can be found at various geographical scales.
The name of the line separating China and tibet is McMahon Line.
Durand Line
The Canadian / United States Border?
The Equator
The name is a meridian. It is located 371 Spanish Leagues west of the Cape Verde Islands.
The coastline
The line separating the numerator and denominator when displayed as one number over another is called Vinculum, or sometimes referred to as the fraction bar. If the line is a slanting line (such as in "9/10"), it's referred to as the solidus.
The sharp line separating the Indomalayan and Australasian ecozones is primarily due to the Wallace Line, a boundary separating the two biogeographic regions based on differences in species composition. The line is formed due to differences in geological history, land connections, and climate patterns, leading to distinct flora and fauna on either side.
It's called a vinculum.
International dateline
A fall line is a place where rivers descend in falls or rivers from a Piedmont to a plain. It's an imaginary line that runs parallel to the east coast of the United States.
The border which separates India and Peoples Republic of China is known as "McMahon line" and was introduced by "Sir Henry McMahon" of the UK.