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A glossary of science-related words.

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maar crater

A distinctive crater that is formed in a phreatomagmatic eruption (where the magma interacts with water). Maar craters are typically wide (around 1 km in diameter) and surrounded by a ring of pyroclastic material.

Mach number

A number that compares the speed of an object with the speed of sound (about 330 m/s or 1200 km/h), for example, Mach 2 is twice the speed of sound.


1. In human nutrition, a nutrient that is required in large amounts and provides the energy needed to maintain body functions and carry out the activities of daily life. There are three macronutrients – carbohydrates, proteins and fats. 2. In agriculture, a macronutrient is any of the chemical elements required by plants in relatively large amounts: carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium, magnesium, sulfur and calcium.

macrophage cells

The cells of the immune system whose main function is to rid the body of dead cells and other debris.


Large soil pore (greater than 0.03 mm) that may result from the biological activity of earthworms or other soil fauna, plant roots or soil cracks.


Molten rock that is found under the Earth and has not reached the surface. Formed from the Earth’s mantle and forms the lava that erupts from volcanoes.

magma chamber

A space under a volcano that stores magma before and between eruptions. Exact composition and role is under review.


A magnetic iron oxide mineral found in many igneous, metamorphic and sedimentary rocks. Magnetite is an important mineral in the black sand found at some New Zealand beaches.

mahinga kai

Generally refers to indigenous freshwater species that have traditionally been used as food, tools or other resources.

main sequence star

Stars that fuse hydrogen into helium. Gravity acting inwards balances gas pressure acting outwards – 90% of stars, including the Sun, are at this stage in their lives.

mainland island

An area of land that has been isolated from the surrounding environment, usually with a predator-proof fence.


An infectious disease caused by protozoa that are transmitted through the bite of an infected Anopheles mosquito.


A medical term used to describe a disease or condition that is likely to cause death or serious disablement unless effectively treated. In skin cancer, a tumour that is cancerous and likely to spread if left untreated.


1. Capable of being shaped or formed. 2. Easily hammered into shape.


The insufficient, excessive or imbalanced consumption of nutrients.


A warm-blooded animal, such as a human being, dog or whale, the female of which produces milk from mammary glands to feed her young/newborn offspring.


An examination of a breast that uses low dose X-rays.


A Māori word relating to authority, control, influence, prestige or power.

mana whakahaere

A Māori phrase referring to the authority that Waikato-Tainui and other Waikato River iwi have over the Waikato River based on their connection to the river.


1. A layer of the inner Earth between the crust and the core. Varies in temperature from 500 °C to 900 °C. Consists of semi-fluid molten rock. 2. A layer in molluscs that covers the fleshy body. In some molluscs, it secretes a shell (for example, snails), but it doesn’t in others (for example, slugs).


A metamorphic rock formed when limestone within the Earth’s crust is subjected to high temperature and pressures over a long time period.


A loose, earthy deposit consisting of a mixture of clay, sand and silt that contains a substantial amount of calcium carbonate.


Acronym for microwave amplification by stimulated emission of radiation. In astronomy, masers are found when water or other substances are excited by radiation from a star or by the energy of a collision. In physics, a maser is a device that amplifies or generates electromagnetic waves, especially microwaves.


The amount of matter an object has, measured in kilograms.

mass extinction

One of several events in the last 500 million years when 50–90% of all species died out. Mass extinctions were ‘rapid’ in geological terms and led to the expansion of new species.

mass number

The sum of protons and neutrons in the nucleus of an atom. For example, C-14 has 6 protons and 8 neutrons in its nucleus, so its mass number is 6 + 8 = 14.

mass spectrometry

An analytical technique measuring the characteristics of individual molecules by converting them to ions.


A star cluster that appears in the early morning sky for the first time in the year in late May or June. It marks the beginning of the Māori New Year.


Customary knowledge.

mātauranga Māori

A contemporary term referring to Māori knowledge, Māori ways of knowing and associated practice.


The basic structural component of all things that have mass and volume.

maximum accepted value (MAV)

The highest level of a hazardous substance that is considered ‘safe’.

mechanical advantage

The ratio of the output force produced by a lever to the applied input force.

mechanical engineering

A branch of engineering that deals with the design, construction and operation of machinery.


A field of physics that studies the action of forces on objects made of matter.


Late stage in the life cycle of a crab. Characterised by the use of abdominal appendages to swim.


A type of cell division that creates gametes (in humans, egg and sperm cells) for sexual reproduction.

Meissner effect

When a superconductor is cooled below its critical temperature, it has the ability to expel an applied magnetic field. This effect can be demonstrated by levitating a small magnet above a suitably cooled superconductor.


The black or dark brown pigments present in the hair, skin and eyes of humans and animals. It is produced in excess in certain skin diseases and in melanomas. People with dark skin have more melanin than people with fair skin.


Cells in the epidermis of the skin and elsewhere that produce melanin.


Cancer of the melanocytes. The cancer usually appears on the skin, but may affect the eye and membranes (for example, the lining of the nose, the meninges of the brain or the lining of the anus).


A transition metal in Group 12 of the periodic table – symbol Hg, atomic number 80.


The geological era from 250 to 65 million years ago made up of the Triassic, Jurassic and Cretaceous periods. Reptiles, mammals, birds and flowering plants developed during this era.


Chemical processes that occur in living organisms, for example, to produce energy, growth or eliminate waste.


Any of a category of elements that usually have a shiny surface, are generally good conductors of heat and electricity and can be melted or fused, hammered into thin sheets or drawn into wires (for example, copper).


An element that exhibits some properties of metals and non-metals. These elements tend to be semiconductors (e.g. silicon).


A material engineered to provide properties that may not be readily available in nature.


The name for rocks that have been changed through heat and pressure in the Earth’s crust, for example, marble, which can be found in the South Island.


The changing of one rock type into another with heat and pressure.


A profound change in form from one stage to the next in the life history of an organism.


Tumours or masses of cells that develop when cancer cells break away from the original (primary) cancer and are carried by the lymphatic and blood systems to other parts of the body.


Shooting star. A meteor is the flash of light in the (usually night) sky when space debris or meteoroids burn up from friction with the Earth’s atmosphere. Note that ‘meteor’ refers to the flash of light, not the actual solid debris.


A piece of matter from space that falls to the Earth’s surface. Most extraterrestrial material is in the form of dust, but larger metallic or rocky meteorites sometimes make it through the Earth’s atmosphere.


Generally, astronomers reserve this term for chunks of space rocks less than 1.6 km in diameter (larger pieces are usually called asteroids). They are thought to be made from asteroid fragments following collision of these larger bodies. Most meteoroids that enter the Earth’s atmosphere vaporise completely because of the friction.

methane gas hydrate

An ice/methane gas mixture in which methane is trapped within a crystal structure of water. Large deposits of this ‘methane ice’ have been found under sediments in the Hikurangi Margin.


A liquid alcohol – chemical formula CH3OH.

methanotrophic archaea

A category of microorganism similar to bacteria that uses methane gas as its energy source.


A disease in babies where their blood is unable to carry enough oxygen. It can be caused by excessive nitrates, often from fertilisers, in drinking water.

metric system

A decimalised system of measurement originating in France. It is formally known as the International System of Units (SI).


A class of scientist involved in the science of measurement. Metrologists develop and evaluate calibration systems that measure characteristics of objects such as length, mass, time, temperature, electric current and luminous intensity as well as derived units such as pressure, speed and electrical resistance.


A microscopic spherical structure, often composed of lipid molecules.


Another name for microorganism. An organism too tiny to see without a microscope, such as bacteria and fungi.

microbial activity or processes

The metabolic activities of microorganisms resulting in chemical or physical changes.


A scientist who studies microorganisms, like protozoans, algae, moulds, bacteria and viruses. They are concerned with the structure, function and classification of these organisms and with ways of controlling and using their activities.


The climate of a small area such as a town or a patch of bush.


In biology, a community represented on a small scale. An experimental system that simulates real-life conditions as closely as possible while allowing the manipulation of environmental factors.


A fossil that is so small that you need a microscope to see it.


A digital image or photograph that represents the view through a microscope.


A distant object in space can be magnified when a massive object, such as a galaxy or star, passes in front of it. The gravity of the ‘lens’ object in front bends light from the object behind.


A type of fixed-wing aircraft that is lightweight and designed to carry one or two people.


A unit of length 1 millionth of a metre (10-6 metre). Also known as a micrometre.


A substance such as a vitamin or mineral that is a necessary dietary component. Although needed in only small amounts, they are essential for health and wellbeing.


An organism too small to see without a microscope. Microorganisms are also known as microbes and include bacteria, viruses, protozoa, yeast and some algae.


A scientist who studies microscopic fossils.


An instrument that uses a lens or a series of lenses to magnify small objects.


Invisible electromagnetic waves with wavelengths ranging from 1 mm to 1 m. Microwaves occur between radio and infrared waves on the electromagnetic spectrum.

mid-ocean ridge

An underwater mountain range, formed by plate tectonics through the uplifting of the ocean floor. This happens when rising magma beneath the oceanic crust pushes the overlaying plates apart creating a rift.


A pile of rubbish found in an archaeological or historic site.

Mifflin equation

A simple equation that can be used to predict resting metabolic rate. It is based on body mass, height, age and sex. Published by nutrition researcher MD Mifflin in 1990.

Milky Way

The galaxy that contains our Solar System.


1. (Geology) A naturally occurring solid formed through geological processes. Any given mineral has a characteristic chemical composition and a specific set of physical properties. 2. (Dietary) An inorganic compound needed for proper body function and maintenance of health, for example, iron in the form of haeme present in red meat.


A geological epoch forming part of the Neogene period that extends over the time division 23–5 million years ago. It follows on from the Oligocene epoch 34–23 million years ago.


Small rod-shaped structures inside cells that are responsible for energy production. They contain a small amount of genetic material, allowing them to make some of their own proteins.


The type of cell division that makes new body cells.

model organism

A non-human species used by scientists to better understand particular biological research questions.


The traditional tattoo of Māori culture. Often applied to the face but also to the body, it is a permanent pattern formed by chiselling ink into the skin.


1. A pigmented spot on the skin that contains a cluster of melanocytes. Also called a nevus. 2. (mol) One of the SI base units, the mole is defined as being the amount of substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon-12.

molecular formula

A chemical formula showing the number and type of atoms present in a molecule of an organic compound, for example, glucose has the molecular formula C6H12O6.

molecular mass

The amount of mass the molecule has, often measured in daltons (Da). One dalton is approximately equal to the mass of one proton or one neutron.


Two or more atoms bonded together. The molecule of an element has all its atoms the same. The molecule of a compound has two or more different atoms.


A large division of invertebrate (without a backbone) animals. The best-known molluscs are snails, slugs, shellfish, octopuses and squids.

moment of a force

An alternative name for torque.


The property of a moving object that keeps it moving until a force changes that motion. Momentum is equal to mass (kg) x velocity (m/s).

monochromatic light

Light of one colour. All wavelengths are the same or confined to a very narrow range. For example, red light visible to the human eye covers the wavelength range from 630–740 nm.


A plant of one of the two major groups of flowering plants (angiosperms) characterised by a seed with one seed leaf called a cotyledon.

monozygotic twins

Identical twins that originate from a single fertilised egg and therefore share identical DNA.


The lower vegetation belt on mountainous areas, which can include anything from forests, shrublands and tussock grasslands.


An important clay mineral that belongs to the 2:1 group of sheet silicates.

mood food

A type of functional food that has the effect of positively altering a person’s mood. For example, the caffeine present in tea and coffee beverages can lead to increased alertness, a feeling of being energised and an elevation of mood.


A u-shaped or semi-circular ridge of rocky debris which marks the end of an earlier glacier limit. The ridge is formed at the front of a glacier and remains after the glacier retreats.


The visible, physical characteristics of an organism.


The outward appearance of an organism.


An extinct type of marine reptile that lived in the Cretaceous period. They looked something like a huge crocodile, with paddles instead of legs. Many different species lived in the sea around New Zealand.


Magnetic resonance imaging (MRI) is a non-invasive diagnostic procedure in which the patient is encircled in a strong uniform magnetic field that interacts with radio waves to excite the nuclei of specific atoms (usually hydrogen). This is translated into a visual image on a computer screen showing detailed internal cross sections of the body.


Methicillin-resistant Staphylococcus aureus, a bacterium responsible for several difficult-to-treat infections in humans.


Abbreviation of Master of Science – a higher degree obtained through classes and research projects. Master’s degrees are also available in other subjects, such as art and business.


The acronym for the Measurement Standards Laboratory.


A type of protein found in human saliva. It is a very effective lubricant, allowing chewing and swallowing to proceed with little damage to the lining of the mouth and oesophagus.


A fine-grained sedimentary rock formed from a mixture of clay and silt. (Silt particles are larger than clay particles.)


Involving a combination of several disciplines.


A member of the lepton family of elementary particles. It is unstable and has similar properties to the electron but with a far greater mass.


The tissue that makes it possible for an animal to move and to maintain its posture. Muscles also make the heart beat, force blood to circulate and move food along the digestive system. The human body has more than 600 muscles.


Capable of inducing a genetic mutation.


To change or alter.


Occurs when the DNA is damaged or changed in such a way that it alters the genetic message carried by that gene.


A close association of two different species that is beneficial to both.


A person who studies fungi, such as mushrooms.


The study of fungi.


A structure formed by the symbiotic relationship between a fungus and a plant. The fungus grows around the small roots of the plant and helps it to absorb minerals from the soil. The plant supplies sugar to the fungus to help it grow.

mycorrhizal mushrooms

Mushrooms that grow in the soil on tree roots. They form a symbiotic (of benefit to both parties) relationship with their plant hosts. The trees benefit from the relationship because the fungus helps with the uptake of essential minerals from the soil, and the tree in return provides the fungus with carbohydrates and a place to live.


The strands that make up muscle fibres. They are made up of even thinner filaments.


The oxygen-transporting and storage protein of muscle.


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