The common causes of cough include,

1)Acute respiratory Infection : Pneumonia,Bronchitis

2)Chronic Respiratory Infection : TB(Pulmonary Tuberculosis), Postnasal drip.

3)Airway disease : Asthma , COPD (Chronic Obstructive Pulmonary Disease).

4)Irritants : Cigarettes Smoking, Inhaled Foreign Bodies.

5)Drug Induced : Inhaled drugs(aerosols), ACE - Inhibitors (Anti-Hypertensive)