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A glossary of science-related words.

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The technology associated with the use of high frequency sounds and the application of this to do work.


Any sound whose frequency is above the range of normal human hearing (greater than approximately 20 kHz). Used in medical fields as an imaging technique and also used by animals in nature for navigation.


Fine structural detail in a biological sample (such as cells or tissue) that can only be seen using a high-resolution electron microscope.

unbalanced force

When the forces pushing an object in one direction are greater than the forces pushing in the opposite direction. Also known as the resultant or net force.


A boundary between layers of rock that marks a period of unrecorded time. This may be when erosion removed rock or when no rock was deposited.


A student who is studying for their first degree, the most common of which is called a bachelor’s degree.


The layer of vegetation (shrubs and plants) between the forest floor and the beginning of the main tree canopy.

universal solvent

A term often used with water because water dissolves more substances than any other solvent. However, water does not dissolve every chemical.


All matter and energy, including the Earth, the galaxies and the contents of intergalactic space, regarded as a whole.

unsaturated fat

The fatty acids present in this type of fat have at least one double bond as well as single bonds present between each of the carbon atoms in the molecule.


A link used to transmit a data signal from a local source to a remote receiver. For satellites, this is the radio connection that carries electromagnetic signals from a ground station up to a satellite.

uranium-lead dating

A type of radiometric dating system that analyses decay chains to find the age of specimens from 1 million years old to over 4.5 billion years.


A chemical compound found in urine. It is a concentrated nitrogen source and is manufactured artificially for use in fertilisers.


A small sensory structure in the inner ear that monitors the tilt of the head by sending nerve impulses to the brain for interpretation.

UV (ultra violet) light

Light that is invisible to the human eye and at a wavelength between 300–400 nanometres. UV light is what causes sun burn and can cause some types of cancer.