The time necessary for one complete double oscillation or roll of a ship as from port to starboard and back to port.

The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties.

Annual, intermediate and special surveys. The purpose of the annual and intermediate surveys is to confirm that the general condition of the vessel is maintained at a satisfactory level.

Permafrost is ground that continuously remains below 0°C (32°F) for two or more years, located on land or under the ocean.

A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field.

Permanent magnet generator (PMG) is a synchronous electrical generator design based on the use of permanent magnets on the rotor.

The electrical motor of the novel type. It promises high powers at relatively low weights. However, it always requires a converter.

After the seal has been in service for some time, the rubber loses some of its elasticity and has a permanent groove visible on the sealing face, measured in mm.

Permeability is the measure of magnetization that a material obtains in response to an applied magnetic field.

There are many different spaces and compartments on board a ship. Some of them could be quite empty, others can house some equipment, and therefore its different parts can be occupied by water in case of flooding.

The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. A PEL is usually given as a time-weighted average (TWA).

A perovskite solar cell is a type of solar cell which includes a perovskite-structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer.

Perpetual motion is the motion of bodies that continues forever in an unperturbed system.

Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection.

A manned, non-self-propelled submersible tethered unit consisting of one or more chambers. All of them are maintained at an internal pressure near one atmosphere.

The method of evacuation from an oil rig in very severe weather conditions. The system consists of a cable car running between a specially equipped support vessel and the oil rig.

Petrochemicals are the chemical products obtained from petroleum by refining.

Petrol engine (British English) or gasoline engine (American English) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels.

Petroleum also known as crude oil and oil, is a naturally occurring, yellowish-black liquid found in geological formations beneath the Earth's surface.

Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes.