Final answer:
Bronchiectasis is the condition where bronchi become enlarged and dilated, often due to infection or injury that impairs mucus clearance and air movement.
Step-by-step explanation:
When the bronchi become enlarged and dilated, this condition is called bronchiectasis. It's a chronic condition that usually results from an infection or other conditions that injure the walls of the airways or prevent the airways from clearing mucus. In bronchiectasis, the damaged bronchi can't properly move air in and out, and they become a breeding ground for bacteria. This differs from bronchitis, which is the inflammation of the bronchi, and from conditions like asthma and COPD (which includes chronic bronchitis and emphysema) where the airways are narrowed due to inflammation, muscle spasms, increased mucus, or alveolar damage, affecting breathing and gas exchange.