Final answer:
Two conditions that must be met for lines to be parallel are that they must have the same slope and they must never intersect.
Step-by-step explanation:
In order to have parallel lines, two conditions must be true: a) They must have the same slope, and b) They must never intersect. Parallel lines are defined by having the same directional orientation and never meeting, regardless of how far they are extended in either direction. A classic example of parallel lines can be found in the opposite sides of a rectangle, which never cross and are always equidistant from each other. On a coordinate plane, parallel lines will always have identical slopes, as slope is a measure of the steepness and direction of a line. If two lines have different slopes, they will eventually intersect at some point, hence cannot be parallel.