At least 4 lines, but no matter how many lines, every line has to be parallel with at least one other line.
2 pairs of parallel lines.
1 pair of parallel line
There cannot be parallel lines in any [plane] triangles.
zero
At least 4 lines, but no matter how many lines, every line has to be parallel with at least one other line.
2 pairs of parallel lines.
There cannot be parallel lines in any [plane] triangles.
1 pair of parallel lines
A cube has exactly 6 parallel lines.
1 pair of parallel line
no lines
Exactly one. No more and no less.
Assume there are no lines through a given point that is parallel to a given line or assume that there are many lines through a given point that are parallel to a given line. There exist a line l and a point P not on l such that either there is no line m parallel to l through P or there are two distinct lines m and n parallel to l through P.