This is a chronic disorder that results in intermittent, reversible airway obstruction:

Asthma is a chronic inflammatory airway disease characterized by intermittent, reversible obstruction of the airways. The obstruction results from a combination of bronchospasm, airway mucosal edema, and increased mucus production triggered by various stimuli such as allergens, exercise, cold air, or infections. Between episodes, many patients have near-normal lung function, which illustrates the reversible nature of the obstruction — a defining feature that distinguishes asthma from other obstructive diseases. Tuberculosis is a chronic bacterial infection caused by Mycobacterium tuberculosis; it primarily affects the lung parenchyma, causing granuloma formation, cavitation, and fibrosis, but is not characterized by intermittent reversible airway obstruction. Croup is an acute viral upper airway condition seen predominantly in young children, causing subglottic edema and a characteristic barking cough; it is not a chronic disorder with intermittent reversible obstruction. Pneumonia is an acute infectious or inflammatory process involving the alveoli and lung parenchyma, causing consolidation; it is not chronic or intermittently reversible in the way asthma is. The key descriptors — chronic, intermittent, and reversible airway obstruction — point specifically to asthma.