Term	Related Terms	Definition	Other synonyms
PA		Protective Antigen. The term may be specifically applied to a component of the anthrax toxin, but any antigen that can stimulate a protective response from the immune system may be called a protective antigen.
Pandemic	Epidemic	An epidemic spread over a wide geographical area, such as a country, a group of countries, or a continent. A pandemic is not necessarily a world-wide event.
Papule, papular		A hard swelling on the skin similar to a pimple or pustule but not containing pus.
Paralysis	Paresis	A loss of the ability to make a voluntary movement, such as walking, picking something up, or even voluntary eye movements.
Paresis	Paralysis	Most often a limited form of paralysis. Sometimes used to describe a general paralysis.
Paroxysm, Paroxysmal		Generally relating to sudden actions. A paroxysm can be a sudden convulsion or spasm. A paroxysmal disease is one with an extremely rapid onset of symptoms. Malaria is often used as an example of this because of the sudden onset of chills associated with the disease.
Pediculicide	Pesticide, Insecticide	A pesticide used to kill lice
Percutaneous	Cutaneous	Moving through the skin.
Persistence		A measure of the time taken for the concentration of a chemical agent to fall off after it has been distributed on the battlefield. Some agents, such as cyanides are relatively non-persistent and can dissappear in minutes. Others, such as VX and mustard gases can represent a significant problem for days or weeks.
Petechia (pl. petechiae)	Hemorrhage	Small discolored spots, often purplish, seen on the skin or mucous membranes as a result of a small hemorrhage.
Peyer's patches	Lymphoid tissue	Patches of lymphoid tissue found on the inner surface of the intestine. Although they normally help to protect against infection, they are used as a point of entry for the agent that causes typhoid.
PF		Protection Factor - a value indicating how effective a barrier or filter may be at protecting the user from exposure to an agent.
Photophobia		Unusual sensitivity to light arising from the effects of disease leading to a sufferer avoiding light.
Phytotoxin		A toxin from a plant, such as ricin.
Piloerection		Hair standing on end.	Goose pimples, goose flesh
pKa		The pH at which a substance that can be ionized in water becomes ionized.
Plasmid	DNA, chromosome	A piece of DNA that can exist in a host cell independently of the host chromosome and that can be transmitted from one organism to another. Plasmids carry genes responsible for their own maintenance and genes that can affect the properties of the host organism. A common property is antibiotic resistance - cells become resistant to an antibiotic when they receive a plasmid. Some plasmids carry toxin genes or genes involved in pathogenesis.	Episome
Platelet, Blood platelet	Clotting, blood clotting, coagulation	A small subcellular particle found in the blood that plays a crucial role in blood clotting and repair of damaged blood vessels.	Thrombocytes
Pleio-	Pleiomorphic	A prefix signifying multiple
Pleiomorphic	Dimorphic	Having multiple forms depending upon environmental conditions. This is distinct from polymorphic which also indicates multiple shapes, but independent of environmental conditions.
Pleura	Pleural effusion, Pleurisy	The thin membranes that cover the outside of the lungs and the inside of the chest cavity. The membranes and the fluid they are bathed in helps to minimize friction as the lungs move within the chest cavity.	Pleural membranes
Pleural effusion	Pleura	An unusual accumulation of fluid in the space between the pleura, or the name for the fluid itself.
Pleurisy	Pleura	Inflammation of the pleura.
Plume		A column of a material moving through the air, such as smoke from a chimney. A plume may be ascending (rising through the air) if the released material is less dense than air, such as cyanide. If the plume is descending it is falling through the air because the material is denser than air, such as mustard gas.
Pneumonia		A filling of the lungs with fluid generated by the body, as opposed to drowning. The fluid is generated in response to an inflammation of the lungs, often by disease, or by chemical irritation and can be seen in exposure to mustard gas, chlorine, or phosgene and occasionally when exposed to high levels of riot control agents.
Pneumonitis	Pneumonia	An inflammation of lung tissue.
Polymerase chain reaction		A method of detecting a DNA sequence, even at very low concentrations, by specifically amplifying it. The method makes use of the structure of DNA and the mechanism by which DNA is replicated to create a large number of copies of a very specific sequence. Amplifications of 100-1000 million fold can be achieved meaning that as few as eight cells can be reliably detected in samples.	PCR
Polyuria	Oligouria	Frequent urination.
PPW		Patient Protective Wrap - a wrapping used to protect patients in a contaminated environment.
Prodrome	Syndrome, Morbidity	The earliest symptoms of a disease that precede the development of the full blown disease or syndrome. A prodrome may be followed by a period of remission before the development of the disease.
Prostration		Extreme exhaustion or weakness.
Proteinuria		The appearance of elevated levels of protein the urine.
Ptosis		Abnormal drooping, especially of the eyelids, that is indicative of muscular weakness.
Pulmonary		Related to the lungs.
Pulmonary cavitation		The formation of cavities (holes) in the lungs as part of a disease. It is most often seen in tuberculosis.
Purulent	Pus	Related to the formation, secretion, or containing of pus.
Pus	Purulent	A yellowish or white, viscous fluid found in infected tissues. It contains cell and tissue debris and white blood cells that have been fighting the infection.
Pustule, pustular	Pus	A pimple: a raised spot on the skin containing pus.