There cannot be a horizontal line in a vertical plane.

All lines in a horizontal plane are horizontal.

Two lines in a plane always intersect in a point.

If two lines intersect at a point $P$, then $P$ is called the point of concurrence of the two lines.

If two lines intersect at a point $P$, then $P$ is called the point of intersection of the two lines.

If $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ are collinear points and $\mathrm{D}, \mathrm{P}$ and $Q$ are also collinear, then points $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}, \mathrm{P}$ and $Q$ are always collinear.

Two different lines can be drawn passing through two given points.

Through a given point only one line can be drawn.

Four points are collinear if any three of them lie on the same line.