A Dowel screw.
a straight angle
Line Segment
The vertex (or apex).
line segment
A Ray
It is a horizontal line segment.
A line with a point at each end is known as a segment. A line with an arrow on each end, however, is known simply as a line.
a straight angle
A line segment with a finite, non-zero gradient.
it's what you call circle
A slim steel shaft with a handle at one end and a point shaped to fit screw heads at the opposite end.
Line Segment
The vertex (or apex).
A ray. Rays have a starting point and no ending. They go on forever.
Abyssal plains
The end would be called a point or an endpoint. It only has one end since it is infinite in the other direction.
The Camera?