How many points do you need in order to name a ray?
O
one
four
о
three
two

You need the starting point, and another point that helps direct where the ray is aimed. Call these two points A and B.

Saying "Ray AB" means we extend a line through AB such that the line goes forever through B and beyond B, but we do not do the same for point A. The point A is effectively a cliff where no road goes on the other side of it. Check out the diagram below to see what I mean. The arrow means the line goes on forever in that direction.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.