bar line
Bar lines divide the staff into measures
The bar line devides the staff into measures.
It is a vinculum
The imaginary line that divides the earth into the northern and southern hemispheres is called Equator, the line that divides it into the eastern and western hemispheres is the prime meridian.
The line that divides the Eastern and Western hemispheres is called the Prime Meridian.
Hemispheric line
It is a line of symmetry.
A bisector
A line which divides a shape in two is called a bisector.
That line is called a "Diameter".
When a line divides another in two equal parts, it is called a bisector. If the bisector happens to cross the other line at right angles, it is called a perpendicular bisector.
vertex ?