PAH or Pah may refer to:
In chemistry and biology:
- Polycyclic aromatic hydrocarbon, one of a class of chemical compounds, organic pollutants
- Phenylalanine hydroxylase, an enzyme involved in breaking down phenylalanine
- Para-aminohippurate, a substance used in the measurement of blood flow in the kidneys
- Pulmonary arterial hypertension, a condition of elevated blood pressure in the pulmonary artery
- Primary alveolar hypoventilation, a condition of inadequate air movement in the lungs
- PAH world hypothesis, hypothesis that proposes that the use of polycyclic aromatic hydrocarbon was a means for the origin of life
- Poly(allylamine hydrochloride), Polyelectrolyte
- PAH clearance, para-aminohippuric acid clearance as a measurement of renal plasma flow
- Polyanhydrides, a class of biodegradable polymers
In fiction:
Other:
