## Parallel Lines

Look carefully and identify if the railroad tracks intersect each other.

The railroad tracks do not intersect each other at any point. The lines that lie in the same plane, do not intersect each other, and are always the same distance apart are called **parallel lines**.

### Parallel Postulate

Consider a line m and plot a point P outside the line. We can draw only one line parallel to the given line passing through the point.

So, m′ is parallel to m and passes through P.

### Skew Lines

The lines that do not intersect each other but lie in different planes are called **Skew lines.**

### Perpendicular Lines

The lines which intersect each other at 90° are called **perpendicular lines.**

#### Perpendicular Postulate

Consider a line m and plot a point P outside the line.

We can draw only one line perpendicular to the given line passing through the point.

### Concept Map

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