In maths, a ray.
A ray is a straight path of points that goes on forever in only one direction. A line would go on forever in two directions.
A keel stabilizes a boat allowing it to go in a straight line (one direction).
A line will normally have two points in it to determine what direction the line is to go. The lines name is the name of the points. A line can have one point but that will not specify which way the line should go.
The first number tells you how far you must go in one direction (by convention, often the horizontal direction); the second number tells you how far you must go in another direction (usually the vertical direction).
Sometimes you do, sometimes you don't. In the Euclidean plane. a straight line is the shortest distance between two points. Also, the equation of a straight line is simpler than that of curved lines. Finally, there is the Occam Rule which can be put as follows: when there are lots of possibilities to choose from, go for the simplest one. There are infinitely many curves (including a straight line) that can go through a pair of points.
Displacement is equal to distance when an object moves in a straight line, without changing direction or backtracking. In this scenario, there is no difference between the distance traveled (total path length) and the displacement (direct line between start and end points).
It would depend on what the angle is, what it is deflected off, and if its all straight then.... South
there is a statue of a Quiggle pointing the direction for you to go if it points up walk up if it points down go down
You must only travel down a one-way street in the correct direction, as indicated by roadside signs.
south
one direction
they "Wanted" to find One direction to go