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 two lines in a plane that are always the same distance apart and never meet or intersect, regardless of how far they are extended.

2. **Definition of Perpendicular Lines**:
- Perpendicular lines are two lines that intersect at a right angle (90 degrees). This means that the angle formed between the two lines is exactly 90 degrees.

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