Spirometry is a vital test used in the diagnosis of lung diseases. It measures the volume of air a person can breathe in and out, and how quickly and efficiently they can do so. Although spirometry is the most commonly used diagnostic test, there are a variety of other synonyms that can be used to describe the same test. These include, but are not limited to: Pulmonary Function Test (PFT), Lung Function Test (LFT), Respiratory Function Test (RFT), Forced Expiratory Volume (FEV), and Peak Expiratory Flow Rate (PEFR). Regardless of the synonym used, the test is pivotal to a patient's care, treatment, and overall health in the management of pulmonary diseases.