Geometry Basics • Topic 2 of 5

Lines

A line is a straight path of points that extends without end in both directions, shown with arrowheads on each end. A part of a line with two endpoints is a line segment, and a part with one endpoint is a ray. In a plane, two lines are either parallel (never meeting, equal slopes), intersecting (crossing at one point), or the same line. Two lines that cross at a right angle are perpendicular. These relationships drive many SAT problems involving angles and coordinate geometry, so it helps to recognise parallel and perpendicular lines quickly and to distinguish a full line from a segment or ray.

Parallel lines beside perpendicular linesLinesparallelperpendicular

✅ Solved examples

1. How far does a line extend?
Without end in both directions.
2. What is a part of a line with two endpoints called?
A line segment.
3. What are two lines in a plane that never meet called?
Parallel lines.
4. Two lines that meet at a 90° angle are called?
Perpendicular lines.

✏️ Practice — try these, take hints as needed

1. A figure that extends forever in both directions is a:
Full straight path.
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Line.
2. A part of a line with two endpoints is a:
Two endpoints.
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Line segment.
3. Lines in a plane that never intersect are:
Same direction.
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Parallel.
4. Lines that cross at a right angle are:
90° meeting.
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Perpendicular.
5. Parallel lines have what relationship between their slopes?
Same direction → same…
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Equal slopes.

📝 Topic test — 8 questions

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