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A glossary of science-related words.

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T cell

A type of immune cell that helps to protect the body by fighting diseases or other harmful substances.

tabular icebergs

A type of iceberg shape with a long flat top and steep sides – often they are quite large. Other types of icebergs are blocky, wedge, pinnacle, drydock and dome.

tangata whenua

A Māori term that literally means ‘people of the land’. It refers to the indigenous people of New Zealand.


1. Something physical that you can touch. 2. Definite.


A transition metal in Group 5 of the periodic table – symbol Ta, atomic number 73.


Within a traditional Māori world view, a taonga is a treasure that represents whakapapa in relation to a kin group’s estate and tribal resources. Amongst many things, a taonga can be a living creature, a landscape, an object or a song. Taonga are important to the mana (honour and prestige) of the iwi associated with them.

taonga tuku iho

Heirlooms, treasures that have been handed down.

Taupō Volcanic Zone

A region of active volcanism that stretches approximately from Tauranga to Taupō in the central North Island. Associated with plate tectonics – the Pacific plate is subducted under the Australian plate.


The plural of taxon, referring to a taxonomic category, such as a phylum, order, family, species or genus.


A person who is involved in taxonomy – the science of classification.


The science of classification; a system of arranging living things into natural, related groups based on some factor common to each.


The co-operative or co-ordinated effort on the part of a group of individuals working together as a team to achieve a common goal, cause or purpose. Teams are usually structured in a defined way with a leader and group members, rules and roles, specific outcomes and timeframes.

tectonic activity

Activity that occurs as a result of tectonic plate movement, for example, earthquakes, volcanoes and mountain building in general.

tectonic plate

One of several large sections of the Earth’s crust. The Earth’s surface consists of six big tectonic plates and several smaller ones.

tectonic plate boundaries

The margin formed when tectonic plates collide. For example, off the east coast of the North Island, the Pacific plate and the Australian plate are colliding, giving rise to the boundary known as the Hikurangi Margin. There are three main types of boundary: convergent, divergent and transform.

temperate limestone

A category of limestone, rich in the mineral calcite, that has formed from the smashed up calcareous skeletal debris of marine organisms (both plants and animals) that once lived in cool or temperate waters of higher latitudes.


A measure of the degree of hotness or coldness of an object. Kelvin scale temperature is a measure of the average energy of the molecules of a body.


Stringy tissue that attaches muscle to bones.


A core belief or principle.


A force tending to stretch or elongate something.

tension stress

A stress state where a body of material is stretched or expanded.


Not certain or fixed.


Scientific term for the ash and rock vented from a volcano. Can accumulate on the landscape after an eruption, which allows scientists to track different eruptions from different volcanoes.


Causing abnormal development.

terminal velocity

The constant speed that an object travels at once the forces acting on it become balanced.


Belonging or from the land. This term is often used to describe plants and animals, meaning they live on the land.


The tesla (symbol T) is a unit that defines the intensity (density) of a magnetic field. The tesla was defined in 1960 in honour of inventor, scientist and electrical engineer Nikola Tesla.


A molecular structural shape in which four atoms or groups of atoms are symmetrically arranged around a central atom. The positions of the four surrounding atoms define the vertices of a tetrahedron.

tetrodotoxin (TTX)

A potent neurotoxin with no known antidote.


A range of treatments that can be used to help the body’s natural defences fight off infectious diseases. They strengthen the immune system to do its job. These include medications (drugs), vitamins, healthy eating, exercise and rest.

thermal energy

All forms of matter have internal or thermal energy. This comes about as a result of particle motion (kinetic energy) as well as the energy stored in chemical bonds present in the particles themselves (potential energy).

thermal equilibrium

A state in which all parts of a system are at the same temperature.

thermal reactor

A nuclear reactor in which nuclear fissions are caused by neutrons that are slowed down by a moderator.

thermal shock resistance

The ability of a material to withstand rapid heating followed by rapid cooling over many cycles.

thermally resistant

A measure of a material's ability to resist heat transfer.

thermic effect

The energy needed by the digestive system to process food for storage and use. About 10% of the energy value of foods consumed is needed to meet this demand.


Process that allows the conversion of heat energy into electrical energy.


A layer of water that has a large variation in temperature from top to bottom. In the ocean, it often separates surface waters from deep waters, both of which have similar temperatures throughout.


The branch of science concerned with heat and its relation to energy and work.


An instrument to measure temperature.

Thermophilic bacteria

Bacteria that thrive at hot temperatures. They have an optimal growth temperature of 45 – 122oC.


The ability of the body when placed under a variety of external conditions to keep its temperature within a safe range.


The force that moves an object forward. For example, the thrust of the engines on an aeroplane keeps it moving through the air.

thyroid gland

A two-lobed endocrine gland located in front of and on either side of the trachea (at the base of the front of the neck), which produces hormones to control our metabolism, growth and development.


Māori customs and traditions that have been handed down from the ancestors.


Soil, clay and rock that has been deposited by glaciers.


A metal – symbol Sn, atomic number 50.

tin disease

The transformation of ordinary white tin into powdery grey tin at very cold temperatures.

tissue biopsy

A tissue biopsy is a medical test where cells or tissues from the area of interest are removed from a living subject for examination. This is usually done with a needle, unless a large lump is being removed and/or the architecture of the tissue has to be preserved. The tissue is usually examined under a microscope as well as being subject to a variety of chemical tests.


A device for producing controlled nuclear fusion. Its design allows for the generation, heating and confinement of extremely hot plasma.


A non-SI unit of mass – 1 tonne = 1000 kg.

tooth enamel

The hardest and most highly mineralised substance of the body. A form of hydroxyapatite is the main mineral present.


The turning or twisting force about a pivot.




The level of harm a toxin can cause.


The study of toxins and toxicity.


A poisonous substance that is a specific product of the metabolic activities of a living organism.

trace element

An element present in an organism in only very small amounts but essential for normal metabolism. Iodine and cobalt are two of several trace elements required by humans.

trace metal

One of a group of metals that occur in extremely small quantities and can be found in animal and plant cells and tissue. Trace metals include iron (Fe), magnesium (Mg), lithium (Li), zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), cobalt (Co), vanadium (V), arsenic (As), molybdenum (Mo) and selenium (Se).


A land plant having a vascular system (for example, ferns, seed plants, lycophytes).


An identifiable substance, such as a dye or radioactive isotope, which can be followed through the course of a mechanical, chemical or biological process. The use of radioactive iodine, for example, can give information about thyroid gland metabolism.

trade winds

A wind that blows almost constantly from east to west and towards the equator. Trade winds are caused by hot air rising at the equator, with cool air moving in to take its place from the north and from the south. The winds are deflected westward because of the Earth’s west-to-east rotation.


A characteristic feature or quality that distinguishes one person (or thing) from another.


An arc (path) made (or likely to be made) by an object, such as a bullet or a launched rocket, as it moves from its launch position to its point of impact. The moving object has had some force applied to it to set it moving on its path.

trans fat

When unsaturated plant oils are treated industrially with hydrogen to make them semi-solid, some of the molecules are converted into a form known as ‘trans’. Trans fats are chemically similar to saturated fats.


The process in which DNA is copied to form a complementary RNA sequence. The first step in protein synthesis.


An imaginary line drawn through an area in order to help scientists sample and monitor organisms or conditions along the line. The results obtained from samples along the line give an indication of the organisms or conditions in the entire area.


In organic chemistry, this is the process of exchanging the alkoxy group of an ester compound with another alcohol. These reactions are often catalysed by the addition of an acid or base. Alcohol + ester (plus a catalyst) turns into a different alcohol + a different ester.


To be given a completely different form or appearance.

transform boundaries

An area where two tectonic plates meet and slide horizontally past each other. Crust is neither produced nor destroyed.


An organism (plant, animal, bacterium or virus) whose genome has been changed using genetic material from a different species.


A semiconductor device commonly used to amplify or switch electrical currents.


When a small object passes across the face of another in space. Most commonly, this is a planet passing across the face of its sun.

transition metals

A group of hard, tough metal elements, which conduct electricity. Includes well known metals such as gold, silver, iron, copper and platinum.


The process in which a messenger RNA (mRNA) sequence is used as a template to form a sequence of amino acids (a protein). Occurs after transcription.


When plants or animals are transported to a new area to establish a new population or to add genetic diversity to an existing population.


A substance that light can pass through easily but that will cause the light to scatter. Objects are not clearly visible when viewed through a translucent substance.

transmission of light

If light falling on an object is allowed to pass through, it is called transmitted light. Objects that allow this to happen are called transparent.


To change or transform from one form, nature, substance or state into another.


A substance that light can pass through without scattering. Objects are clearly visible when viewed through a transparent substance such as smooth window glass or water.


The process by which water exits leaves in plants and enters the atmosphere in a gas phase.


A device that receives a signal at one frequency and retransmits it at a different frequency.

transuranium element

An element with an atomic number greater than 92.


Also called oil traps. This refers to accumulations of petroleum that cannot escape sideways (laterally) or upwards (vertically) because of a geological feature (such as folds or faults) that contain layers of rock material that are impermeable, meaning the oil cannot seep through.


A type of limestone formed as a result of the precipitation of calcium carbonate from carbonate-rich spring waters, which are often hot (hot springs).

trigeminal sense

A combination of taste and smell that detects chemical irritants in the mouth/throat area, recognising them as flavour. The trigeminal nerve is the fifth cranial nerve.

triple point of water

The three phases of water are liquid water, solid ice and gaseous water vapour. They can only exist together in equilibrium at a temperature of 0.01 °C or 273.16 K and a pressure of 611.73 Pa. This point is known as the ‘triple point’ of water and is an unchanging property of water.

trophic level

The feeding level in food webs. For example, producers are in the first trophic level.

tropical limestone

A category of limestone, rich in the mineral aragonite, that has formed in warm tropical waters either from marine organisms, such as reef-building corals, or from chemically precipitated grains of calcium carbonate.


The lowest layer of the Earth’s atmosphere. We live in the troposphere. All weather happens in this layer.


A series of massive waves generated in the ocean usually by earthquakes, volcanic eruptions or submarine and coastal landslides, but they can also be caused by the impact of meteorites from outer space.


A thickened underground stem, for example, a potato. A tuber stores food so the plant can lie dormant over winter and is a way of producing new plants asexually.


Tuberculosis or TB (short for tubercle bacillus) is a common but often deadly bacterial infection that primarily affects the lungs.


Abnormal growth of tissue.


Māori term for ancestors.


A measure of water clarity. High turbidity may occur when sediments are disturbed or other particles are suspended in the water.

turbulent flow

The swirling motion of air (or other fluids) caused as an object moves through it. Turbulent flow is created when the airflow separates from the surface of an object.

type 2 diabetes

A chronic (lifelong) disease marked by high levels of sugar (glucose) in the blood. It is caused by the body responding incorrectly to insulin, which is needed to move blood sugar into cells.