Glossary

A glossary of science-related words.

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absolute dating

Finding the actual dates of geological or archaeological objects. Normally expressed as calendar years ago.

absolute zero

The lowest possible temperature, equivalent to -273.15 °C. Used as the zero point of the Kelvin temperature scale.

absorption of light

When the incident light energy striking a material object is completely taken in by the atoms/molecules that make up the structure of the object.

acceleration

The rate at which an object speeds up, slows down or changes direction.

accelerometer

A device to measure acceleration (the rate at which an object’s velocity changes).

accommodation

The process by which the eye changes the shape of the crystalline lens to maintain a clear image of an object as its distance from the eye changes.

accuracy

In science, accuracy indicates the closeness of the measurements to the true or accepted value.

actin

A type of protein that makes up the thick filaments in a myofibril.

active site

Any location on the surface of a molecule that reacts with another molecule.

actuator

A machine that is used to create an automatic and regular action in something.

adaptation

An alteration or adjustment in structure or habits, which is often hereditary, by which a species or individual improves its condition in relationship to its environment.

additive mixing

The mixing of the primary colours of light (red, green and blue) to create other colours. For example, mixing red and green light produces yellow light.

adenosine triphosphate (ATP)

A chemical used by cells to store and transport energy.

adhesion

A binding force that allows unlike particles or surfaces to cling to one another.

adjuvant

An agent that is added to vaccines. It stimulates the immune system and increases the response to the vaccine.

adsorption

The binding of molecules or particles to a surface. This is different from absorption – the filling of pores in a solid. Adsorption is usually weak and reversible.

advanced ceramics

Substances based on metal oxides like alumina (Al2O3), inorganic non-metal oxides like silica (SiO2) and nitrides like silicon nitride (Si3N4). Unlike traditional clay-based ceramics (pottery), advanced ceramics do not necessarily need to be earth-derived.

aerobic

Respiration that uses oxygen.

aerobic capacity

Ability to use oxygen to provide energy.

aerodynamic drag

The force that acts against the motion of an object as it moves through the air. Also known as wind resistance or air resistance.

aerodynamics

The study of how air flows over and through objects and the forces generated by the flow.

aerofoil

A specially shaped structure designed to produce lift for flight. It usually refers to a wing that is curved and narrows to a sharp trailing edge.

aestivate

(Also written as estivate.) To spend a dry, hot season in an inactive, dormant state.

agar plate

A sterile Petri dish that contains a jelly-like growth medium called agar (plus some nutrients), which is extracted from seaweed and used to culture microorganisms such as bacteria.

aggregate

A collection of items gathered together to form a total quantity, for example, soil clumps together to form aggregates. Small aggregates can clump together to form larger aggregates called peds.

agricultural lime

Ground-up limestone, rich in calcium carbonate, that is spread on pasture and added to soils to increase the pH of the soil. It also provides a source of calcium and improves the uptake by plants of major plant nutrients.

air particles

The structural components of air. It includes gas molecules such as oxygen and nitrogen as well as larger dust, pollen and ash particles.

air pressure

The force exerted by the weight of a column of air over a given surface area.

air resistance

The forces that oppose the relative motion of an object through air. Also known as drag.

albedo

The proportion of solar radiation that is reflected by the Earth’s surface, typical for white surfaces (i.e. snow, ice, clouds).

algae

A large and diverse group of simple plants that contain chlorophyll and can therefore photosynthesise.

algal bloom

A rapid increase or accumulation in the population of algae in an aquatic system.

alkaloids

A group of naturally occurring chemical compounds, which mostly contain basic nitrogen atoms.

allele

An alternative form of the same gene that occupies the same location on a chromosome.

allergy

A disorder of the immune system; a hypersensitivity to the reintroduction of an allergen. Allergic reactions occur to normally harmless substances.

alloy

A mixture of a metal with one or more other elements to modify its metallic properties, for example, brass is an alloy of copper and zinc.

alluvial

Land that has been built up from soil or sediments deposited by a river or other running water.

alpha particle

High-energy helium nucleus emitted during certain nuclear decay processes.

alpine habitats

Living or growing above the timberline.

alternation of generations

A life cycle in which there are two stages – typically a spore-producing sporophyte generation and a gamete-producing gametophyte generation.

alumina

The chemical compound aluminium oxide (Al2O3). Heat treatment of alumina yields a tough, hard-wearing ceramic used to make dental and surgical implants.

amalgam

A mixture of metals based on mercury.

amino acid

The basic building block of proteins. A short chain of amino acids is called a peptide, and a long chain of amino acids (normally more than 50) is called a protein.

ammonia

A compound of nitrogen and hydrogen with the formula NH3. It is a colourless gas with a characteristic pungent smell.

ammonite

An extinct marine mollusc with a coiled shell, related to squid, which became extinct at the end of the Cretaceous period, 65 million years ago.

ammonium

NH4+. Derived from ammonia by combination with a hydrogen ion. A nitrogen compound taken up by plants from soils.

amoeba

A primitive singled-celled animal.

ampere

The SI base unit of electric current. It is defined as that current in two very long parallel wires 1 metre apart that gives rise to a magnetic force per unit length of 2 x 10-7 N/m.

amphibian

A class of animals that includes frogs, toads, salamanders and newts.

amphipod

A type of very small crustacean with no carapace and generally with a laterally compressed body.

amplifier

Something, natural or technological, that produces an output greater than the input.

amplitude

The maximum displacement from the equilibrium on an energy wave (i.e. the size of the wave).

amylase

An enzyme present in saliva that can digest starch.

anaerobic

Respiration that does not use oxygen.

anaerobic capacity

Ability to provide energy without using oxygen.

anatomical

Relating to the structure of living things.

andesite

A type of rock that contains moderate amounts of silica and iron. Includes rocks such as scoria. Associated with cone volcanoes or stratovolcanoes. Mt Taranaki and Mt Tongariro are examples of andesite volcanoes.

anecic

Greek for ‘out of the Earth’. Earthworms occupying the anecic niche live as far as 3 metres below the soil surface.

aneurysm clip

An aneurysm is a localised, blood-filled dilation of a blood vessel or cardiac (heart) chamber caused by disease or weakening of the vessel or chamber wall. A ruptured aneurysm results in haemorrhage and is often fatal. Doctors can use clips placed across the aneurysm to stop the blood escaping.

angiosperm

A flowering plant whose seeds are enclosed within an ovary (for example, an apple or a rose).

angle of attack

In aerodynamics, the angle at which the wing meets the airflow. If correctly angled, the result is the force of lift.

angle of incidence

The angle between a light ray incident on a flat surface and an imaginary line (called the normal) perpendicular to the surface at the point of incidence.

angle of reflection

The angle between the reflected ray moving away from a flat surface and an imaginary line (called the normal) perpendicular to the surface at the point of reflection.

angstrom

A unit of length 10-10 metre or 1 ten-millionth of a millimetre. Named after the Swedish scientist Anders Jonas Ångström.

anisotropic

Having properties that differ according to the direction of measurement.

Antarctic Fronts

Regions of water in the Southern Ocean that are organised by temperature and salinity, the boundaries between them are called fronts (see also Subantarctic Front (SAF) and Antarctic Polar Front (APF).

Antarctic treaty

Originally signed by 12 countries, the Antarctic Treaty is now a collection of documents signed by over 40 countries. These contracts explain how Antarctica can be used for things like science and tourism and the types of things that cannot be done in Antarctica (such as military use or mining).

antenna

In physics, a device used to transmit or receive electromagnetic signals such as for radio or television. Also know as an aerial. A satellite dish is a type of antenna.

anther

Contains the pollen sacs of a plant and is the region where pollen is produced.

antheridia

(Singular: antheridium) Multicellular structures in plants where male gametes form.

anti-matter

An alternative form of matter in which each particle has the same mass and properties as their counterparts but with opposite electrical charges. For example, the electron has an antiparticle called a positron. When they meet, an annihilation event occurs, resulting in the formation of gamma rays.

anti-venom

A biological product used in the treatment of venomous bites or stings.

antibiotic

A substance produced by an organism that kills bacteria.

antibody

A protein that attaches to and then destroys or neutralises harmful foreign substances in the body. Part of the immune system.

antidote

A remedy to counteract the effects of poison.

antigen

A substance that, when introduced into the body, stimulates the production of an antibody.

antioxidant

A chemical substance that prevents oxidation by chemical means. Dietary antioxidants present in foods, like vitamins A, C and E, can assist the body to resist the damaging effects of reactive free radicals produced by the body’s metabolic processes.

antiproton

An antiparticle corresponding in mass and properties to a proton but negatively charged and with the opposite magnetic moment. When an elementary particle (such as an electron, proton or neutron) and its antiparticle (such as a positron, antiproton or antineutron) collide, they destroy each other in a process known as annihilation, usually creating photons (light).

anus

The opening to the outside at the end of the large intestine, through which faeces are egested.

apatite

A group of phosphate minerals found in some igneous and metamorphic rocks. One form of apatite, calcium phosphate, is a major component of bones and teeth.

Apgar

Immediately after birth, newborns are given an Apgar score. This score evaluates the health of the newborn based on appearance, pulse, grimace, activity and respiration. The score ranges from 0 to 10.

aphelion

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 maximum distance from the Sun.

apogee

The point in the elliptical orbit of a satellite about the Earth at which the satellite is furthest from the Earth.

apoptosis

A form of cell death in which a programmed sequence of events leads to the elimination of cells without releasing harmful substances into the surrounding area.

aposematic colouration

The recognisable markings of an animal that serve to warn off potential predators.

appendix

A blind-ended tube, about 10 cm long, that runs out from the caecum just below the ileocaecal valve. Its functions are not yet fully understood.

aquaculture

The farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants.

aquifer

A layer of permeable rock or sand that contains water. An aquifer may be freshwater or saline (containing saltwater).

aragonite

A mineral form of crystalline calcium carbonate similar to calcite. It is found in the shells of marine invertebrates such as pāua and in living coral reefs.

arboreal

Living in trees.

archae

Single-celled microorganisms that often live in extreme environments. They look like bacteria but biochemically and genetically are very unlike bacteria.

archegonia

(Singular: archegonium) Multicellular structures in plants where female gametes form.

arsenic

A naturally occurring element that is highly toxic to most organisms.

artefact

1. A product of human art and workmanship. 2. An object remaining from a particular period. 3. In the context of the international prototype kilogram (IPK), a 1 kilogram cylinder of platinum-iridium alloy was manufactured in France in the 1880s to serve as the mass standard. 4. Something observed during a scientific investigation that is not naturally present but has been introduced as a result of the experimental procedure. Artefacts are commonly introduced during preparation of specimens for microscopy.

arteries

Blood vessels carrying blood away from the heart.

arthropod

Phylum containing many animal species including spiders, crabs and all insects. This Greek word means jointed foot or leg, a characteristic feature of all insects, along with segmented bodies and hard exoskeleton.

asbestos

Naturally occurring mineral fibre (silicate) used commercially for its desirable physical properties. The inhalation of asbestos fibres can cause cancer.

ascorbic acid

A water-soluble sugar acid with antioxidant properties. It is commonly known as vitamin C.

asexual reproduction

A way of producing new organisms from a parent without the fusion of sex cells. Offspring are genetically identical to each other and to their parent.

assay

An experiment that is carried out to detect the presence of a chemical or living organism, or to determine the amount of a chemical or living organism.

asteroid

A celestial lump, hundreds of kilometres wide, composed of rock and iron, that orbits the Sun. Most asteroids lie in a belt between the orbits of Mars and Jupiter and are thought to be left-over bits from the formation of the Solar System.

asthma

A common chronic inflammatory lung disease. It is an allergic disease caused by an immune disorder.

astrobiologist

A scientist who considers what life on other worlds might be like and looks for environments that could support life on planets, other than Earth, in and beyond the Solar System.

astrophysicist

An astronomer who studies the physics of the universe and things in it.

astrophysics

The study of physical aspects of stars, galaxies and the universe, such as temperature, gravity and light.

atmosphere

1. The layer of gas around the Earth. 2. (atm) A non-SI unit of pressure equivalent to 101.325 kPa.

atmospheric pressure

The force per unit area at a given location on the Earth caused by the weight of the air above it. At sea level, this pressure is about 10 N per cm2 (101.3 kPa in SI units).

atom

The smallest possible unit of matter that still maintains an element’s identity during chemical reactions. Atoms contain one or more protons and neutrons (except hydrogen (H), which normally contains no neutrons) in a nucleus around which one or more electrons move.

atomic clock

Caesium atomic clocks operate by exposing caesium atoms to microwaves until they start to vibrate at one of their resonant frequencies. By measuring this frequency, which is an unchanging property of matter, a time measure can be established. Caesium atomic clocks are very stable, and accuracies of 1 second in 1.4 million years have been reported.

atomic force microscope

An instrument that uses a tiny probe to ‘feel’ a surface and map its atoms.

atomic mass

The average mass of all isotopes of an element, taking their natural relative proportions into account. For example, chlorine has two main isotopes – 37Cl and 35Cl. In naturally occurring chlorine, 75% is 35Cl and 25% is 37Cl. Therefore, the weighted average (atomic mass) is 35.5.

atomic number

The number of protons in the nucleus of an atom. This determines an element’s properties and location on the periodic table of elements.

atomistics

A study of something at the atomic level – a study of its atoms.

Auckland volcanic field

An area of basaltic volcanism in Auckland city that is not associated with a tectonic plate boundary. It includes about 50 volcanoes over an area of 360 square kilometres.

aurora

Also known as the northern or southern lights, auroras are an atmospheric phenomenon that results in multi-coloured light shows in the night sky near the polar regions.

autism

A developmental disorder that usually appears in childhood and is characterised by emotional detachment and a limited ability to socially interact and communicate. Sufferers can also have an extremely limited range of activities and interests.

Auto-immune disease

A disease that arises from an overactive immune response of the body against a normally harmless substance that enters the body.

autotroph

An organism that is able to make its own food.

avatar

A movable image that represents a person in a virtual reality environment.

aviation

The design, development, production, operation and use of aircraft, especially heavier-than-air aircraft.

aviatrix

A female aviator or person who flies an aircraft.

Avogadro constant

A fundamental physical quantity (symbol NA or L) representing the molar number of entities. It has the value 6.022 141 5 x 1023 mol-1.

awa

Māori word for river.

axon

A long extension from a neuron that transmits signals to other cells.