pulmonology
Pulmonology is the branch of medicine that looks after the lungs and the rest of the breathing apparatus. If you imagine the body as a house, the pulmonologist is the specialist for its ventilation system: the pipes that carry air in and out, and the place where fresh air finally meets the blood.
More formally, pulmonology is the internal-medicine subspecialty devoted to the respiratory system and the diagnosis, treatment and prevention of diseases of the airways, lungs and the lining around them. It spans common problems such as asthma, chronic obstructive pulmonary disease, pneumonia, lung cancer, sleep apnea and tuberculosis, as well as rarer scarring and vascular diseases of the lung.
Pulmonology overlaps with several neighbouring fields. It shares critical-care medicine (the intensive-care unit and the ventilator), thoracic surgery (operations on the chest), and parts of cardiology, infectious disease, oncology and allergy. In much of the world the very same specialty is called respirology or respiratory medicine; the names differ by country, but the subject is the same.
Pulmonology is mostly a medical (non-surgical) specialty; operations on the chest are usually done by thoracic surgeons, with whom pulmonologists work closely.