Py

Pylon
The tower above a bridge deck that usually carries cable stays.
Pyramid
In ancient Egypt, a quadrilateral masonry mass with steeply sloping sides meeting at an apex, used as a tomb.
Pyranometer
An instrument which measures global radiation, the combined intensity of direct solar radiation and diffuse sky radiation.
Pyrex Glass
A type of glass that is resistant to heat and chemical attack. Often used in cookware and in laboratory equipment.

Pyrgeometer
An instrument which measures the effective terrestrial radiation.
Pyrheliometer
An instrument which measures the intensity of direct solar radiation.
Pyrheliometry
The science and study of pyrheliometric measurements.
Pyroclastic
Fragmented rock material formed by a volcanic explosion or ejection from a volcanic vent.
Pyroclastic Flow
A hot, dry, fast-moving (10-100m/s) and high-density mixture of ash, pumice, rock fragments, and gas formed during explosive eruptions or from the collapse of a lava dome.
Pyroclastic Surge
Turbulent, low-density cloud of hot rock debris and gases that moves over the ground surface at high speed. Lower density than Pyroclastic Flow.
Pyroelectricity
Electric charge produced as a material undergoes a temperature change.
Pyrolyser
An instrument that breaks complex molecules into constituents by using heat.
Pyrolysis
Thermal degradation of waste in the absence of air to produce char, pyrolysis oil and syngas.
Pyrometer
A device for measuring the high temperatures in a furnace.
Pyrometric Photography
The derivation of flame temperature measurements by means of comparative photography with a calibrated light source.
Pyron
A unit of radiant intensity of electromagnetic radiation equal to 1 calorie per square centimeter per minute.
Pyrophoric
Catches fire spontaneously when exposed to air at normal room temperature.
Pythagoras
Greek philosopher and mathematician; held that numbers were basic to matter.
Pythagoras Theorem
The Square on the Hypotenuse is equal to the sum of the squares of the other two sides.
Pythagorean Triangle
A right triangle whose sides are integers.
Pythagorean Triple
An ordered set of three positive integers (a,b,c) such that a2+b2=c2.