Give a definition for each of the following terms. Are there other terms that need to be defined first? What are they, and how might you define them?(i) parallel lines (ii) perpendicular lines (iii) line segment   (iv) radius of a circle (v) square.

Explanation

### Step-by-Step Text Solution

1. **Definition of Parallel Lines**:
- Parallel lines are lines in a plane that do not intersect or meet at any point, regardless of how far they are extended. They maintain a constant distance apart.

2. **Definition of Perpendicular Lines**:
- Perpendicular lines are lines that intersect at a right angle (90 degrees). When two lines cross each other and form an angle of 90 degrees, they are said to be perpendicular.

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