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Glossary

A glossary of science-related words.

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Glossary terms A–Z definitions

P-waves

Seismic waves that travel as compressions (similar to how sound travels). They can travel through solid and liquid.

A fortified Māori village or settlement.

paleo-ocean circulation

Historic ocean current systems.

paleoecologist

Someone who studies fossils of plants and animals in order to reconstruct past ecosystems.

paleoecology

A branch of science that studies fossils of plants and animals in order to reconstruct past ecosystems.

Paleogene

The geological period after the Cretaceous, lasting from 65 to 24 million years ago. Divided into the Paleocene, Eocene and Oligocene epochs.

paleomagnetic dating

A type of dating method that examines the way magnetic iron particles are oriented in a sample and compares this with known movements of the magnetic North Pole over geologic time.

paleomagnetism

Changes in the Earth’s magnetic field recorded by the way magnetic minerals lined up in rocks as they were formed.

paleomagnetist

A scientist who studies past changes in the Earth’s magnetic field.

paleontologist

Someone who studies fossils of plants and animals.

paleoseismology

Study of past earthquakes.

palladium

A transition metal in Group 10 of the periodic table – symbol Pd, atomic number 46. A silvery-white, ductile, malleable metal discovered in 1803, used as a catalyst.

pancreas

A greyish-pink organ, about 15 cm long, that stretches across the back of the abdomen, behind the stomach. It produces hormones such as insulin and glucagon (endocrine function) as well as pancreatic juice that contains digestive enzymes (exocrine function).

pandemic

A global outbreak of disease.

paradigm

An example or pattern underlying a theory or methodology.

paramagnetic

Very weakly attracted by the poles of a magnet but not retaining any permanent magnetism.

paramagnetism

A form of magnetism that occurs only in the presence of an externally applied magnetic field. Paramagnetic materials are attracted to magnetic fields, but they do not retain any magnetisation in the absence of an externally applied magnetic field.

parasites

Plants or animals which live in or on another plant or animal, drawing nutriments (food requirements) from its host. Parasites usually cause harm to the host.

parasitism

A close association of two different species where one organism harms its host organism.

parasitology

The study of the biology of parasites.

Parkinson’s disease

A degenerative disorder of the central nervous system that often impairs the sufferer's motor skills and speech.

particle

A tiny piece of matter. A particle may refer to an atom, part of an atom, a molecule or an ion.

particle accelerator

A device, such as a cyclotron or linear accelerator, that accelerates charged subatomic particles or nuclei to high energies. Also called an atom smasher.

particulates

Fine particles of a liquid or a solid suspended in a gas, for example, the visible soot suspended in smoke.

pascal

(Pa) Derived SI unit of pressure – 1 pascal = 1 newton per square metre.

patent

A document granting an inventor sole rights to an invention.

pathogen

A disease-causing organism.

pathogenic

An organism that causes disease. Certain types of bacteria are pathogenic to humans – they cause diseases such as food poisoning. Some fungi are pathogenic to plants – they cause diseases such as potato blight.

pāua

Large edible sea snails that are found around the coastline of New Zealand. They grow large shells that, when polished, have a blue, green and purple iridescent appearance.

pearl

A semi-precious gemstone of calcium carbonate produced in the mantle of a living shelled mollusc such as an oyster.

peer review

The evaluation of work or performance by other people in the same field in order to maintain or enhance the quality of the work or performance.

pelagic

Marine species that live in the upper layers of the open sea or lake.

penicillin

A type of antibiotic produced by the fungus Penicillium.

penstock

A gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems.

peptide

Two or more amino acids linked together to form a chain.

peptide bond

A covalent bond found in proteins and polypeptides that links amino acids together.

peptide hormone

A hormone made up of a short chain of amino acids (polypeptide). For example, antidiuretic hormone is a nine amino acid polypeptide produced by the pituitary gland in the brain to control urine production in the kidney.

perigee

The point in the elliptical orbit of a satellite about the Earth at which the satellite is closest to the Earth.

perihelion

The point in the elliptical orbit of an object (such as a planet or comet) about the Sun at which the object is at its closest distance to the Sun.

periodic table

The organisation of all known elements into groups with similar properties.

periostracum

A thin mainly protein layer that is the outermost part of the shell of molluscs such as pāua and mussels.

peristalsis

An organised contraction and relaxation of gut wall muscles that has a wave-like motion. It is an automatic and important process that moves food through the digestive system and can sometimes be felt in the abdomen as gas moves along.

permeable

A surface that allows fluids and gases to pass through.

perpendicular

At right angles (90 degrees).

pesticide

A substance or mixture of substances used for preventing, controlling, or lessening the damage caused by an unwanted organism (a pest).

petrochemical

A chemical substance obtained from petroleum or other fossil fuels such as coal or natural gas.

petrography

The scientific description of the composition and formation of rocks.

petroleum geologist

A scientist who studies all aspects of oil discovery and production.

pH

A measure of the acidity or alkalinity of a solution.

phage (bacteriophage)

A virus that infects bacteria.

phantom (breast)

A silicon model of a real breast that mimics certain properties that a real breast has. In this case, the phantom is mimicking the stiffness of the breast tissue. The silicon model has a known stiffness, and the team can insert various objects into the phantom that mimic tumours that also have known stiffness values. They can then test their techniques to see if the stiffness images they are producing match up with the known stiffness of the phantom.

PhD

Abbreviation of Doctor of Philosophy – a degree normally obtained after a concentrated period of research. This is the highest level of degree that involves supervision by academic staff at a university.

phenolic glycocide

A chemical compound that can be extracted from plants. It is said to possess antiseptic properties.

phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetic make-up and environmental influences.

phloem

The vascular tissue that serves as a path for the distribution of food material in a plant.

phosphate minerals

Minerals (inorganic salts) of phosphate all contain the same structural tetrahedral unit (PO4). Examples are apatite (Ca5(F,Cl,OH)(PO4)3), triphylite (LiFePO4) and lithiophilite (LiMnPO4).

phosphor

A substance that emits light when excited by electromagnetic radiation.

phosphorus

A chemical element with the symbol P and atomic number 15. Phosphorus is essential for life, playing a critical role in cell development and in producing ATP, DNA and lipids in plants and animals.

phosphorus cycle

Phosphorus, which is essential for life, is found in rocks. From there, it cycles through water, sediments and soil. In soil, it is made available to plants (and animals through plants). As organisms decay, it is cycled back through water, sediments and rocks.

phosphorus immobilisation

A process in which the activities of microbes convert plant-available phosphorus into forms not available to plants.

phosphorus mineralisation

A process in which the activities of microbes convert organic forms of phosphorus into inorganic forms that can be used by plants.

phostrex

A fire suppression agent developed for aviation applications.

photoaging

Skin damage caused by ultraviolet rays.

photoelectric effect

Given the right conditions, when light with sufficient energy is shone onto a metal surface, electrons can be emitted or ejected from the surface of the metal. The energies of the emitted electrons are independent of the intensity of the incident light.

photokeratitis

A painful eye condition caused by too much light burning the cornea, for example, from using a welder’s torch or tanning beds without eye protection. Feels like having sand poured into the eyes.

photometer

An instrument that measures the brightness (intensity) of light.

photon

A discrete bundle (or quantum) of electromagnetic (or light) energy. Photons are always in motion and, in a vacuum, have a constant speed of light to all observers, at the vacuum speed of light (more commonly just called the speed of light) of c = 2.998 x 108 m/s.

photoreceptor

A specialised structure or cell that is sensitive to light. The retina at the back of the eye contains two different structural types of photoreceptor – rods and cones.

photosynthesis

A process in green plants and some microorganisms that changes carbon dioxide and water into carbohydrates using the energy in sunlight. The process often releases oxygen into the atmosphere as a byproduct.

photovoltaic (PV) cells

Layers of semiconductor materials in contact with each other and fitted with metallic contacts to transfer the released electrons to the external load. Most commercial photovoltaic cells are manufactured from crystalline silicon.

photovoltaics

A method to convert sunlight directly into electricity by using solar cells packaged in photovoltaic modules.

phreatomagmatic

A type of volcanic explosion where the emerging magma meets water (either groundwater or seawater), causing a violent eruption. The water becomes superheated while the magma is rapidly chilled.

phylogenetic

The systematic study of the relationships of groups of organisms based on evolutionary similarities and differences.

phylum

A division used in the Linnean system of classification or taxonomy.

physical metallurgy

The engineering and science behind the making of products out of metals.

physiology

The biochemical or physical functions of organisms.

phytochemical

One of a group of biologically active compounds that are found in small amounts in fruits and vegetables. These compounds have been linked to human health by contributing to protection against degenerative diseases such as cancer.

phytomining

Using plants to extract minerals from soil or mine waste.

phytoplankton

Very small plant organisms that drift with water currents and, like land plants, use carbon dioxide, release oxygen and convert minerals to a form animals can use.

pigment

Any fine, insoluble, dry, solid particles used to give colour. In biology, the dye-like material produced generally in the superficial parts of animals that gives colour to skin, eyes and hair.

pinnae

The basic divisions of a (fern) frond.

pistil

The name for all the female reproductive organs (carpels) in a flower. There may be one or more carpels in a pistil.

pitch

1. (Flight) The movement of the nose (front) of an airplane or spacecraft up or down about a transverse axis. 2. (Sound) A human perception of how high or low the frequency of the sound being heard appears to be.

pivot

The point about which a part of the body rotates that is usually a joint.

pixel

A contraction of ‘picture element’. In a medium-sized plasma display flat-screen TV, there are over 900 000 tiny cells called pixels. Each pixel is made up of three gas-filled cells that emit either red, blue or green light when electrically stimulated.

placebo

A substance, usually a pill, having no pharmacological effect (it has no active medicinal ingredients in it). Placebos are sometimes used as a control in testing new medicines, where one person is given the real medicine and another not.

Planck constant

(h) A fundamental physical constant named in honour of German physicist Max Planck who discovered a relationship between the energy carried by a ‘packet’ of radiation and its frequency. E = hf, where E is the energy of the packet, f is the frequency of the radiation and h is the Planck constant (h = 6.626 x 10-34 Js).

planet

In our Solar System, a planet is defined as an object that orbits the Sun, is big enough for its own gravity to make it ball-shaped and keeps space around it clear of smaller objects.

plankton

A group of marine organisms including single-celled and multi-celled organisms.

plasma

A substance that is a form of ionised gas where some of its particles are ionised giving rise to free-moving electrons and ions. It is the fourth state of matter. It is affected by magnetic fields and has high electrical conductivity

plastic

A synthetic material made from a wide range of organic polymers (such as polyethylene, PVC and nylon) that can be moulded into shape while soft and then set into a rigid or slightly elastic form.

plasticise

To be changed into plastic.

plate boundary zones

Tectonic broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.

platinum

A transition metal in Group 10 of the periodic table – symbol Pt, atomic number 78.

Pleistocene

A recent geological epoch – part of the Neogene period. It lasted from 1.81 million years ago until the start of the Holocene 10 000 years ago.

podocarp

Evergreen tree of the Southern Hemisphere of the genus Podocarpus having a pulpy fruit with one hard seed. For example, miro, mataī and tōtara are all podocarp trees.

poison

A substance that, through its chemical action, usually kills, injures or impairs an organism.

poisonous

Capable of harming or killing by or as if by poison.

polar molecule

A molecule such as water that has a slight positive charge on one end and a slight negative charge on the other.  

polar orbit

A type of orbit around the Earth where a satellite passes over each of the poles.

polarised light

Light made up of waves that all oscillate in the same direction.

pollen

Dust-like grains that contain male sex cells (gametes) of flowering plants (angiosperms) and cone plants (gymnosperms). Pollen is made on the anthers of flowering plants.

pollination

The transfer of pollen grains from the anther to the part of the plant containing the ovules. This process is necessary for fertilisation and reproduction of the plant.

pollinator

Something that carries pollen from one flower to another.

polychromatic

Light that is made up of more than one colour.

polychromatic hydrocarbons

Also known as polycyclic aromatic hydrocarbons (PAH). A large group of compounds deriving from crude oil and coal. A common contaminant of soil.

polymer

The name given to a family of chemical compounds with a high molecular weight that have a long chain of smaller, identical linked molecules (called monomers). Cellulose is a naturally occurring polymer, although there are many manmade polymers such as nylon. Polymers are especially valued by many industries where they are the essential ingredient of plastics, concrete, glass and rubber. The process by which molecules are linked together to form polymers is called polymerisation.

polymerase chain reaction (PCR)

A method that rapidly increases the number of copies of a target DNA sequence enabling it to be visualised. Can be used for detecting small amounts of DNA material.

polypeptide chain

A chain of amino acids linked together by peptide bonds.

polyphenol

One of a particular group of phytochemicals found in fruits and vegetables.

porcelain

A very hard, translucent white ceramic. Because porcelain was associated with China and often used to make plates, cups, vases and other works of fine art, it often goes by the name of ‘fine china’.

porous

Containing pores, holes or cavities which may be connected (high porosity) or not well connected (low porosity).

positive feedback loop

In a positive feedback loop, changes accelerate the overall system while a negative feedback loop results in a slowing down.

positron

A particle with the same mass and size of charge as an electron, but it has a positive charge – a positive electron.

post mortem interval

The time that has elapsed since a person has died.

post-mortem

Literally ‘after death’ – it usually refers to an examination of a corpse in order to determine cause of death.

postgraduate

A student who has obtained a first degree and is now working towards a higher degree such as master’s or PhD.

potash

Mined and manufactured salts that contain potassium in water-soluble form. Potash is the common term for fertiliser forms of the element potassium (K).

poultice

A soft moist mass, often heated and medicated, that is spread on cloth over the skin to treat an aching, inflamed part of the body. Also called a cataplasm.

power

The rate at which work is done (defined as work divided by time taken).

powered flight

Flight that is maintained through the use of an engine that propels the craft forward to sustain lift.

ppt

Abbreviation for parts per thousand. For example, if there are 34 g of salt in 1000 g of seawater, this is written as 34 ppt.

precipitation

1. The formation of an insoluble solid (precipitate) from a given solution by altering either its temperature, concentration or chemical composition. 2. In meteorology, this term describes the formation of rain, hail, snow or ice in the atmosphere.

precision

The closeness that repeated measurements show under unchanged experimental conditions.

predator

An animal that kills and eats other animals, called its prey.

preening

To smooth or clean feathers with the beak or bill.

pressure

The force per unit area that acts on the surface of an object.

pressure dissolution

The dissolving of mineral-based grains in a sediment as a result of pressure applied to them through compaction. Once in the pore water, these minerals can then be precipitated out of solution, effectively cementing the grains together.

pressure drag

A type of drag caused by the difference in air pressure between the front and back surfaces of an object as it moves through the air (or other fluid).

primary cilium

A single protrusion from the surface of eukaryotic cells. Primary cilia are thought to sense the extracellular surroundings by detecting mechanical and biochemical stimuli.

primary colours of light

These are three colours of light (red, green and blue) that can be blended to allow us to perceive other colours.

primary colours of pigments

These colours cannot be made from mixing other colours. Primary colours are the source of other colours. The primary colours are red, blue and yellow. Mixing red and blue makes violet, mixing red and yellow makes orange, and mixing yellow and blue makes green.

pristine

Remaining free from dirt or decay; clean.

private science

Those scientific activities, techniques and practices carried out before science is made public science.

producer

An organism that makes its own food from inorganic matter.

profile drag

Also known as wind resistance, profile drag is caused by movement of an object through the air. It is more pronounced at higher speeds and is lowered by streamlining.

prokaryote

A group of organisms whose cells do not contain cell organelles. This group includes bacteria and archae.

propeller

A type of fan that transmits energy by converting rotational motion into thrust. A pressure difference is produced by an aerofoil-shaped blade, and air or water is accelerated behind the blade.

property

A physical or chemical property is a physical or chemical state of a substance that can be measured. Any changes can be used to describe transformations between states.

protease

A class of enzymes that break proteins down into smaller units.

protein

Any of a large class of complex compounds that are essential for life. Proteins play a central role in biological processes and form the basis of living tissues. They have distinct and varied three-dimensional structures. Enzymes, antibodies and haemoglobin are examples of proteins.

protist

Simple eukaryotic organisms that include protozoa and algae.

proton

Elementary particle with a single positive electrical charge.

prototype

A trial working model or preliminary version of something. Sometimes a prototype might be smaller than the final version of an engineered object, so that the engineers can check if the design works before committing themselves to large-scale commercial production.

protozoa

Microscopic, single-celled organisms.

Proxima Centauri

The nearest star to the Sun, 4.2 light years from Earth. It is the faintest of three stars that make up the star system called Alpha Centauri.

pseudo-scientific

A methodology, belief, or practice that is claimed or made to appear to be scientific but lacks appropriate scientific methodology, supporting evidence or scientific status.

psi

Pounds per square inch (psi) is a non-SI unit of pressure – 1 psi = 6.895 kilopascals.

psychoactive drug

A chemical substance that acts primarily upon the central nervous system where it affects brain function, resulting in changes in perception, mood, consciousness, cognition and behaviour.

psychologist

A person trained and educated to perform psychological research, testing, and therapy.

psychrometer

An instrument that allows for the simultaneous readings of wet bulb and dry bulb thermometers. The difference in readings allows a calculation of the relative humidity of air to be made.

public science

Science as communicated in journals, conferences, textbooks and news releases.

pulse net

An international real-time network where pathogen strains are identified and reported.

pulsed field gel electrophoresis

A technique designed to separate large fragments of DNA by ‘pulsing’ a current of electricity in alternate directions to DNA in a gel matrix.

pumice

A type of rhyolite rock found in New Zealand, particularly in the central North Island. It is light in colour, not heavy and often filled with holes.

pupa

An insect in the inactive stage of development (when it is not feeding) intermediate between larva and adult.

pyloric sphincter

A muscular valve that controls the release of food from the stomach into the duodenum.

pyroclastic

Material from a volcano vent that falls back to Earth travelling at great speed, often for some distance. Composed of rock (tephra) and gas, it can move at supersonic speed. Once it cools, it stops moving and solidifies.

PYY

A peptide hormone released by cells in the ileum and colon in response to feeding. It is involved in the regulation of appetite.

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