Chronic progressive interstitial lung disorder characterized by the replacement of the lung tissue by connective tissue, leading to progressive dyspnea, respiratory failure, or right heart failure. Causes include chronic inflammatory processes, exposure to environmental irritants, radiation therapy, autoimmune disorders, certain drugs, or it may be idiopathic (no identifiable cause). The disease is Monarch Disease Ontology term MONDO_0002771 (pulmonary fibrosis). Also known as: fibrosis of lung, pulmonary interstitial fibrosis.