because
line is a group of points
Two lines are intersecting if they have exactly one point in common.
No, you could define a plane as comprising only two lines.
They are both lines that define the tropics. Without any of them, the tropics would not exist.
It would be the difference between the two darker lines, or index lines, and then divide the space in between with your difference.
I would say following the letter address, space two lines for the date, then another two lines for a reference (if applicable) then two lines following that comes the saluation. Between the letter address and the saluation, I would say at least four lines
Yes.To help visualize, consider this:A 3-legged stool won't wobble on a flat surface (3 points of contact.)The minimum number of points to define two intersecting lines is where the point where the lines intersect, and another unique point on each line. (3 points total) This is represented by where the 3-leg stool touches the flat surface. The flat surface represents any determinant plane.If the lines did not intersect, you would require 4 separate points to define them. This is represented by 4-leg chairs, which by contrast often wobble (if only very slightly), since the extra point is not required to define the flat surface that it rests on (the determinant plane)In essence, 'a plane is determined by two intersecting lines' is the same as saying 'a plane is determined by three uniquepoints', which are, in both cases true.
You would have to define that more closely. Where is the boundary between north and South Asia.
Time between an event and a reference time (usually zero)
Without wishing to overcomplicate matters, one could simply define a straight line as: "the shortest distance between two given points".
How would you define a subtancebased on what you have obsrved
How would you define a subtancebased on what you have obsrved