Not necessarily. That only happens in isosceles and equilateral triangles.
a line that intersects an edge of a triangle that is perpendicular to it and passes through the midpoint
and is perpendicular to the opposite side.
The segment that passes through a vertex and is perpendicular to the opposite side is called the altitude of the triangle.
perpendicular
side
Altitude.
No, the perpendicular bisector of a side of a triangle does not necessarily pass through the opposite vertex. The perpendicular bisector is a line that is perpendicular to a segment at its midpoint, and it may intersect the interior or exterior of the triangle, depending on its shape. In fact, the only time a perpendicular bisector passes through the opposite vertex is in the case of an isosceles triangle, where the two sides are equal, and their perpendicular bisectors coincide with the altitude.
A median of a triangle is a line or segment that passes through a vertex and the midpoint of the side opposite that vertex. The median only bisects the vertex angle from which it is drawn when it is an isosceles triangle.
Those would be perpendicular bisectors. If you do that to each side of the triangle they all meet at what is called the circumcenter. http://mathworld.wolfram.com/Circumcircle.html
A line that is perpendicular to the segment of a plane and passes through the midpoint.
A bisector is a line (or line segment) which passes through the midpoint. You can have multiple lines intersect at this one point, and all of them will bisect the original line segment, since they pass through its midpoint. A perpendicular bisector passes through the midpoint, and also is perpendicular to the original line segment, so there will be only one of those.
Always true. To see this draw the circle which passes through the three points of the triangle. Reproduce the reflection of the triangle on the hypotenuse (which passes through the centre). Then use the theorem of intersecting chords of a circle to give the result immediately. It's also simply proved by algebra.