circulation of blood between the heart and the lungs
polarisation
Noun
the phenomenon in which waves of light or other radiation are restricted in direction of vibration
polarisation
Noun
the condition of having or giving polarity
polymorphism
Noun
(biology) the existence of two or more forms of individuals within the same animal species (independent of sex differences)
polymorphism
Noun
(chemistry) the existence of different kinds of crystal of the same chemical compound
polymorphism
Noun
(genetics) the genetic variation within a population that natural selection can operate on
potential difference
Noun
the difference in electrical charge between two points in a circuit expressed in volts
potential drop
Noun
the difference in electrical charge between two points in a circuit expressed in volts
pogonip
Noun
a dense winter fog containing ice particles
potential energy
Noun
the mechanical energy that a body has by virtue of its position
pressure level
Noun
the force applied to a unit area of surface
particle beam
Noun
a collimated flow of particles (atoms or electrons or molecules)
prevailing wind
Noun
the predominant wind direction
puff of air
Noun
a short light gust of air
programmed cell death
Noun
a type of cell death in which the cell uses specialized cellular machinery to kill itself
particulate radiation
Noun
a stream of atomic or subatomic particles that may be charged positively (e.g. alpha particles) or negatively (e.g. beta particles) or not at all (e.g. neutrons)
parhelic circle
Noun
a luminous halo parallel to the horizon at the altitude of the sun
parhelic ring
Noun
a luminous halo parallel to the horizon at the altitude of the sun
parhelion
Noun
a bright spot on the parhelic circle
proton magnetic resonance
Noun
resonance of protons to radiation in a magnetic field
pea-souper
Noun
a heavy thick yellow fog
phosphorescence
Noun
a fluorescence that persists after the bombarding radiation has ceased
photoelectricity
Noun
electricity generated by light or affected by light
piezoelectricity
Noun
electricity produced by mechanical pressure on certain crystals (notably quartz or Rochelle salt)
piezoelectric effect
Noun
electricity produced by mechanical pressure on certain crystals (notably quartz or Rochelle salt)
piezo effect
Noun
electricity produced by mechanical pressure on certain crystals (notably quartz or Rochelle salt)
pleochroism
Noun
the phenomenon of different colors appearing when certain crystals are viewed from different directions
paramagnetism
Noun
materials like aluminum or platinum become magnetized in a magnetic field but it disappears when the field is removed
pleomorphism
Noun
(biology) the appearance of two or more distinctly different forms in the life cycle of some organisms
pleomorphism
Noun
(chemistry) the existence of different kinds of crystal of the same chemical compound
polarization
Noun
the phenomenon in which waves of light or other radiation are restricted in direction of vibration
polarization
Noun
the condition of having or giving polarity
peat moss
Noun
any of various pale or ashy mosses of the genus Sphagnum whose decomposed remains form peat
plant kingdom
Noun
(botany) the taxonomic kingdom comprising all living or extinct plants
plant cell
Noun
a cell that is a structural and functional unit of a plant
plantlet
Noun
a young plant or a small plant
pileus
Noun
a fruiting structure resembling an umbrella or a cone that forms the top of a stalked fleshy fungus such as a mushroom
peridium
Noun
outer layer of the spore-bearing organ in many fungi
poudrin
Noun
small crystals of ice
podetium
Noun
an organ or body resembling a stalk
plant order
Noun
the order of plants
pot plant
Noun
a plant suitable for growing in a flowerpot (especially indoors)
pleurocarp
Noun
a moss having the archegonium or antheridium on a short side branch rather than the main stalk
pleurocarpous moss
Noun
a moss having the archegonium or antheridium on a short side branch rather than the main stalk
prevailing westerly
Noun
the winds from the west that occur in the temperate zones of the Earth
parallax
Noun
the apparent displacement of an object as seen from two different points that are not on a line with the object
pond pine
Noun
large three-needled pine of sandy swamps of southeastern United States
progymnosperm
Noun
an ancestral fossil type from which modern gymnosperms are thought to have derived
pecopteris
Noun
Carboniferous fossil fern characterized by a regular arrangement of the leaflets resembling a comb
pteridophyte
Noun
plants having vascular tissue and reproducing by spores