Parallel Lines:

Lines which never meet at any point and maintain same distance between them.

Transversal Line:

A line which intersects 2 or more lines at distinct points. Different angles are formed at those points.

Types of Angles:

• Acute Angle (angle value between 0° & 90°)
• Right Angle (angle is exactly 90°)
• Obtuse Angle (angle value between 90° & 180°)
• Reflex Angle (angle value between 180° & 360°)

Other such angles are

• Straight Angle (angle is exactly 180°, which is a straight line)
• Complete Angle (angle is exactly 360°, which is a straight line)

Types of Related Angles:

• Complementary Angles (sum of 2 angles = 90°)
  
• Supplementary Angles (sum of 2 angles = 180°)
  m + n = 180° | n + o = 180° | o + p = 180° | p + m = 180°
  q + r = 180° | r + s = 180° | s + t = 180° | t + q = 180°
  
• Alternate Interior Angles (2 angles, on opposite sides of a transversal line inside 2 parallel lines, are equal)
  r = p | q = o
• Alternate Exterior Angles (2 angles, on opposite sides of a transversal line outside 2 parallel lines, are equal)
  t = n | s = m
• Corresponding Angles (2 angles, on the same relative position of 2 parallel lines along a transversal line at each intersection points, are equal)
  m = q | n = r | o = s | p = t
• Vertically Opposite Angles (2 angles, which are on vertically opposite sides at the same intersection point, are equal)
  m = o | n = p | q = s | r = t