seizure disorder Progeroid syndromes, a group of rare diseases causing premature aging Pulmonary stenosis or pulmonic stenosis, obstruction of the pulmonary artery of the heart Physics and chemistry P or static pressure, in fluid mechanics and aviation Proton Synchrotron, a 1959 particle accelerator at CERN Chloropicrin, a highly toxic chemical compound Phosphatidylserine, a phospholipid Phosphorothioate (or thiophosphate), a family of compounds and anions with the general chemical formula PS4−xOx3− (x = 0, 1, 2, or 3) Polystyrene, a common type of plastic Ps, positronium, pseudo-chemical symbol Transportation Paddle steamer, abbreviated PS in vessel prefixes Pacific Southwest Airlines (1949-1988), IATA designator of former airline Ukraine International Airlines, IATA airline designator since 1992 Other uses iPhrothiya yeSiliva, a South African military award MoMA PS1, an art institution in New York Padma Shri, an Indian civilian award Plastic Surgery, abbreviated as P.S. for simple use Police sergeant Power Stage, a World Rally Championship special stage Professional services, abbreviated P.S. in name suffixes State school or public school, in the USA and other countries See also P.S. I Love You (disambiguation) PSS (disambiguation)