Science in plain language

Key-word glossary

A quick explanation, with a route back to the topic.

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Abiotic factor: A non-living factor in the environment, such as light or temperature. Habitats and adaptations →
Absorption: Movement of digested nutrients through the gut wall into the blood or lymph. Digestion and nutrition →
Acceleration: The change in velocity each second, measured in m/s². Motion, speed and acceleration →
Accuracy: How close a measurement is to the accepted value. Measurements, tables and graphs →
Acid: A substance that produces hydrogen ions in water and forms a solution with pH below 7 at room temperature. Acids, bases and pH →
Activation energy: The minimum energy needed for a successful reaction. Energy changes in reactions →
Adaptation: An inherited feature that helps survival and reproduction in a particular environment. Evolution and natural selection →
Aerobic respiration: Chemical reactions that use oxygen to release energy from nutrients. Photosynthesis and respiration →
Alkali: A base that dissolves in water. Acids, bases and pH →
Alveolus: A tiny air sac in the lungs where gases pass between air and blood. Breathing and gas exchange →
Anomaly: A result that does not fit the overall pattern. Measurements, tables and graphs →
Area: The size of a surface, measured in square units such as cm². Measurement and density →
Artery: A blood vessel that carries blood away from the heart. The heart and circulation →
Asexual reproduction: Reproduction from one parent without gametes joining. Inheritance and variation →
Atom: The smallest unit of an element. Atoms, elements and compounds →
Atomic number: The number of protons in an atom’s nucleus. The periodic table and formulae →
Average speed: Total distance travelled divided by total time taken. Motion, speed and acceleration →
Axial tilt: The slant of a planet’s axis from the upright position relative to its orbit. Planets, seasons and the Moon →
Balanced forces: Forces that give a resultant of zero. The object’s velocity does not change. Forces, weight and pressure →
Base: A substance that reacts with and neutralises an acid. Acids, bases and pH →
Big Bang model: The explanation that the Universe expanded and cooled from an early hot, dense state. The Universe and our Solar System →
Biodegradation: Breakdown of a material by living organisms. Materials and sustainability →
Biodiversity: The variety of genes, species and ecosystems. Biodiversity and food production →
Biotic factor: An effect of living organisms, such as competition or predation. Habitats and adaptations →
Capillary: A tiny, thin-walled blood vessel where substances pass between blood and cells. The heart and circulation →
Carbon store: A place where carbon is held, such as the atmosphere, an ocean, a forest or rocks. The water and carbon cycles →
Carbon transfer: Carbon moving from one store to another, for example through feeding, respiration or burning. The water and carbon cycles →
Catalyst: A substance that speeds up a reaction without being used up overall. Chemical reactions and rates →
Cell: The smallest unit that carries out the processes of life. Cells and living things →
Cell membrane: The thin boundary that controls what enters and leaves a cell. Cells and living things →
Chemical digestion: Using chemical reactions to break large food molecules into smaller ones. Digestion and nutrition →
Chemical formula: Symbols and small numbers that show which elements are present and their amounts. The periodic table and formulae →
Chemical property: How a substance reacts to form new substances, such as rusting or burning. Properties of materials →
Chemical reaction: A change that rearranges atoms to make new substances. Chemical reactions and rates →
Chloroplast: A plant-cell structure containing chlorophyll, where photosynthesis happens. Photosynthesis and respiration →
Chromosome: A structure made of DNA that carries many genes. Inheritance and variation →
Climate: The usual patterns of weather in a place over many years. Energy resources and climate →
Closed system: A system that matter cannot enter or leave. Particles and states of matter →
Community: The populations of different species living in the same area. Habitats and adaptations →
Competition: The struggle for a limited resource needed by more than one organism. Habitats and adaptations →
Composite: A material made by combining different materials to get useful properties. Properties of materials →
Compound: A substance made of two or more different elements chemically joined in a fixed ratio. Atoms, elements and compounds →
Condensation: Water vapour changing into liquid water. The water and carbon cycles →
Conduction: Energy passing through a material without the material flowing from place to place. Heat, light and sound →
Conductivity: How easily a material carries electric current or transfers heat. Properties of materials →
Constant velocity: Motion at the same speed in the same direction. The acceleration is zero. Motion, speed and acceleration →
Consumer: An organism that gets food by eating other organisms or their products. Food webs and ecosystems →
Control variables: Factors we keep the same to make a test fair. Planning an investigation →
Convection: Energy transfer by the movement of a liquid or gas. Heat, light and sound →
Correlation: A link between two quantities in the data. This alone does not prove that one causes the other. Measurements, tables and graphs →
Current: The amount of electric charge passing a point each second. Measured in amperes (A). Electricity and circuits →
Cytoplasm: The jelly-like material in a cell where many chemical reactions happen. Cells and living things →
Decomposer: An organism that breaks down dead organisms and waste. Food webs and ecosystems →
Demand: The amount of electrical power users need at a particular time. Technology and electricity choices →
Density: The mass in each unit of volume. Calculate it by dividing mass by volume. Measurement and density →
Dependent variable: The factor we observe or measure. Planning an investigation →
Design criterion: A measurable requirement that tells you whether a design does its job. Power and energy devices →
Diaphragm: The sheet of muscle below the lungs that helps move air in and out. Breathing and gas exchange →
Diffusion: The overall movement of particles from a higher concentration to a lower concentration. Breathing and gas exchange →
Digestion: Breaking large food molecules into smaller molecules that the body can absorb. Digestion and nutrition →
Displacement: The volume of water pushed aside when an object is put completely under water. Measurement and density →
Dissipation: Energy spreading into the surroundings, usually by heating, so it is harder to use again. Energy and conservation →
Distance: The total length of the path an object travels. Motion, speed and acceleration →
Distance-time gradient: The slope of a distance–time graph. For total distance travelled, it gives the speed. Motion, speed and acceleration →
Distillation: Separating and collecting a liquid by boiling it and then cooling its vapour. Mixtures and separation →
DNA: The molecule that carries genetic information. Inheritance and variation →
Double circulation: The two linked routes of blood: heart to lungs and heart to body. The heart and circulation →
Durability: How well a material lasts during use. Properties of materials →
Eclipse: When one body blocks sunlight from reaching another body or an observer. Planets, seasons and the Moon →
Ecosystem: Living organisms and their non-living surroundings interacting together. Food webs and ecosystems →
Ecosystem service: A benefit people receive from natural ecosystems. Biodiversity and food production →
Efficiency: The fraction of input energy that becomes useful output, usually given as a percentage. Energy and conservation →
Egestion: Passing undigested material out of the body as faeces. Digestion and nutrition →
Electrical power: The rate of electrical energy transfer. Calculate it by multiplying voltage by current. Power and energy devices →
Electron: A negatively charged particle found around the nucleus. Atoms, elements and compounds →
Element: A pure substance made of only one type of atom. Atoms, elements and compounds →
Endothermic reaction: A reaction that takes in energy from its surroundings. Energy changes in reactions →
Energy: The ability to bring about changes such as movement or heating. Measured in joules (J). Energy and conservation →
Energy flow: The transfer of energy through an ecosystem and out to the surroundings. Food webs and ecosystems →
Energy profile: A diagram showing the energy of reactants, products and the energy hurdle between them. Energy changes in reactions →
Enzyme: A biological catalyst that speeds up reactions in living things. Chemical reactions and rates →
Ethical question: A question about fairness, responsibilities or what we should do. Exploring space →
Evaluation: Comparing test results with what a design was meant to achieve. Power and energy devices →
Evaporation: Liquid water changing into water vapour at its surface. The water and carbon cycles →
Evidence: Observations or measurements that support or question an explanation. Models, evidence and communication →
Evidence: Observations or measurements that support or question an explanation. The Universe and our Solar System →
Evidence-based decision: A choice supported by relevant observations, measurements and other reliable information. Biodiversity and food production →
Evolution: A change in a population’s inherited characteristics over generations. Evolution and natural selection →
Exothermic reaction: A reaction that releases energy to its surroundings. Energy changes in reactions →
Fertilisation: The joining of sperm and egg nuclei to form a zygote. Human reproduction →
Filtration: Separating an insoluble solid from a liquid using a filter. Mixtures and separation →
Food web: Several food chains linked together. Food webs and ecosystems →
Force: A push or pull that can change an object’s motion or shape. Measured in newtons (N). Forces, weight and pressure →
Friction: A force between touching surfaces that opposes sliding or the start of sliding. Forces, weight and pressure →
Fuel: A substance used to release useful energy, usually by burning. Energy changes in reactions →
Galaxy: A very large group of stars, gas, dust and other matter held together by gravity. The Universe and our Solar System →
Gamete: A sex cell, such as a sperm or an egg. Human reproduction →
Gas: A state of matter with no fixed shape or volume. Particles and states of matter →
Gas exchange: Movement of oxygen and carbon dioxide between the lungs and the blood. Breathing and gas exchange →
Gene: A section of DNA that helps determine a characteristic or controls a cell process. Inheritance and variation →
Generation: Producing electrical energy from another energy source. Technology and electricity choices →
Glucose: A simple sugar used in respiration and to make other substances. Photosynthesis and respiration →
Graph gradient: The change up a graph divided by the change across it. Measurements, tables and graphs →
Gravitational energy: Energy stored when an object is raised in a gravitational field. Energy and conservation →
Greenhouse effect: The warming caused when gases absorb infrared radiation and emit some of it back towards Earth’s surface. Energy resources and climate →
Grid: The network that carries electricity from generators to users. Technology and electricity choices →
Group: A vertical column in the periodic table. The periodic table and formulae →
Habitat: The place where an organism lives. Habitats and adaptations →
Habitat loss: The destruction or change of places that organisms need to live. Biodiversity and food production →
Health: Physical, mental and social wellbeing. Health and microbes →
Heating: Energy moving from a hotter object or region to a cooler one. Heat, light and sound →
Hypothesis: A possible explanation that can be tested using evidence. Planning an investigation →
Immune response: The body’s defence against pathogens and other harmful material. Health and microbes →
Implantation: The embedding of an early embryo in the lining of the uterus. Human reproduction →
Improvement: A change that makes a design work better, supported by the results of a new test. Power and energy devices →
Independent variable: The factor we deliberately change in an investigation. Planning an investigation →
Indicator: A substance that changes colour in acidic or alkaline solutions. Acids, bases and pH →
Inherited variation: Differences between organisms that can be passed from parents to offspring. Evolution and natural selection →
Kinetic energy: Energy an object has because it is moving. Energy and conservation →
Length: Distance between two points, usually measured in metres (m), centimetres (cm) or millimetres (mm). Measurement and density →
Lifecycle: The stages a product goes through, from obtaining raw materials to reuse, recycling or disposal. Materials and sustainability →
Lifecycle impact: An effect of making, using, maintaining or disposing of a product. Technology and electricity choices →
Light-year: The distance light travels in one year. The Universe and our Solar System →
Limiting factor: The factor that is holding back the rate of a process. Photosynthesis and respiration →
Liquid: A state of matter with a fixed volume but no fixed shape. Particles and states of matter →
Mass: The amount of matter in an object, measured in kilograms (kg) or grams (g). Measurement and density →
Mass number: The total number of protons and neutrons in one atom. The periodic table and formulae →
Mechanical digestion: Breaking food into smaller pieces, for example by chewing. Digestion and nutrition →
Menstrual cycle: The repeating changes in the ovaries and uterus, including ovulation and menstruation. Human reproduction →
Microorganism: A living organism too small to see clearly without a microscope. Health and microbes →
Mitigation: Action to reduce the causes of climate change, such as cutting greenhouse-gas emissions. Energy resources and climate →
Model: A simplified representation used to explain or predict something. Models, evidence and communication →
Moon phase: The shape of the sunlit part of the Moon that we can see from Earth. Planets, seasons and the Moon →
Natural selection: The process in which helpful inherited characteristics become more common over generations. Evolution and natural selection →
Net gas exchange: The overall gas movement after taking all gas-producing and gas-using processes into account. Photosynthesis and respiration →
Neutralisation: A reaction between an acid and a base. Acids, bases and pH →
Neutron: A particle in the nucleus with no electrical charge. Atoms, elements and compounds →
Non-renewable resource: An energy resource used much faster than nature replaces it. Energy resources and climate →
Nucleus: The cell structure that contains genetic information and helps control the cell. Cells and living things →
Orbit: The path of one object around another because of gravity. Planets, seasons and the Moon →
Orbit debris: Old satellites, rocket parts and other unwanted objects or fragments left in orbit. Exploring space →
Organ: A structure made of different tissues working together. Cells and living things →
Ovulation: The release of an egg from an ovary. Human reproduction →
Parallel circuit: A circuit with separate branches for the current. Electricity and circuits →
Particle model: An explanation of matter using tiny moving particles. Particles and states of matter →
Pathogen: An organism or infectious agent that causes disease. Health and microbes →
Peer review: Other specialists checking a scientific report before it is published. Models, evidence and communication →
Period: A horizontal row in the periodic table. The periodic table and formulae →
pH: A scale showing how acidic or alkaline a solution is. Acids, bases and pH →
Photosynthesis: The process in which plants use light energy to make glucose from carbon dioxide and water. Photosynthesis and respiration →
Physical change: A change in which no new substance is made. Particles and states of matter →
Physical property: A feature that can be measured without making a new substance, such as density. Properties of materials →
Placenta: The organ through which a developing baby receives oxygen and nutrients and loses wastes. Human reproduction →
Plasma: The liquid part of blood that carries cells and dissolved substances. The heart and circulation →
Pollination: The transfer of pollen from an anther to a stigma, allowing fertilisation to follow in flowering plants. Biodiversity and food production →
Population: Organisms of one species living in a particular area. Evolution and natural selection →
Potential difference: The energy transferred for each coulomb of charge between two points. Also called voltage; measured in volts (V). Electricity and circuits →
Power: Energy transferred each second. Measured in watts (W); 1 W = 1 J per second. Power and energy devices →
Precipitation: Water falling from clouds as rain, snow or hail. The water and carbon cycles →
Precision: How close repeated measurements are to each other. Measurements, tables and graphs →
Pressure: Force acting at right angles to a surface divided by its area. Measured in pascals (Pa). Forces, weight and pressure →
Producer: An organism that makes its own food, usually using light energy. Food webs and ecosystems →
Product: A substance made in a chemical reaction. Chemical reactions and rates →
Proton: A positively charged particle in the nucleus of an atom. Atoms, elements and compounds →
Prototype: A model built to test a design idea. Power and energy devices →
Quadrat: A frame used to mark a sample area in a habitat. Habitats and adaptations →
Radiation: Energy transfer by electromagnetic waves. It can happen through empty space. Heat, light and sound →
Raw material: A resource used to make a product, such as timber or metal ore. Materials and sustainability →
Reactant: A substance present at the start of a chemical reaction. Chemical reactions and rates →
Reaction rate: How quickly a chemical reaction happens. Chemical reactions and rates →
Recycling: Processing waste material to make new products. Materials and sustainability →
Red blood cell: A blood cell that carries oxygen using haemoglobin. The heart and circulation →
Reliable health evidence: Health information supported by trustworthy sources and well-conducted investigations. Health and microbes →
Remote sensing: Collecting information about something from a distance. Exploring space →
Renewable resource: An energy resource that nature replaces quickly enough for continued human use. Energy resources and climate →
Repeat: Another measurement made under the same conditions. Measurements, tables and graphs →
Resistance: How strongly a component opposes current. Calculate it by dividing voltage by current; measured in ohms (Ω). Electricity and circuits →
Respiration: Chemical reactions in cells that release usable energy from nutrients. Breathing and gas exchange →
Resultant force: The overall force when all the forces on an object are combined. Forces, weight and pressure →
Reuse: Using an item again without breaking it down into raw material. Materials and sustainability →
Risk control: An action that reduces the chance or seriousness of harm. Planning an investigation →
Risk factor: Something that changes the chance of a health outcome. Health and microbes →
Rotation: Spinning about an axis. Planets, seasons and the Moon →
Satellite: An object that orbits another body. It may be natural or made by people. Exploring space →
Saturated solution: A solution in which no more solute will dissolve at that temperature. Mixtures and separation →
Scientific benefit: New scientific knowledge or a better way to investigate a question. Exploring space →
Scientific theory: A broad scientific explanation supported by a large amount of evidence. Models, evidence and communication →
Selection pressure: An environmental factor that affects survival or reproduction. Evolution and natural selection →
Sensor circuit: A circuit that responds to a change such as a change in light level or temperature. Electricity and circuits →
Series circuit: A circuit with one path for the current. Electricity and circuits →
Sexual reproduction: Reproduction in which two gametes join. Inheritance and variation →
Solar System: The Sun and the planets, moons, asteroids, comets and other objects that orbit it. The Universe and our Solar System →
Solid: A state of matter with a fixed shape and volume. Particles and states of matter →
Solubility: The maximum amount that dissolves in a given amount of solvent at a stated temperature. Properties of materials →
Solute: The substance that dissolves in a solvent. Mixtures and separation →
Solution: A mixture formed when a solute dissolves in a solvent. Mixtures and separation →
Solvent: The liquid in which a solute dissolves. Mixtures and separation →
Sound: A vibration that travels through a material such as air, water or a solid. Heat, light and sound →
Source evaluation: Checking where information comes from and whether its evidence is reliable. Models, evidence and communication →
Space probe: A spacecraft without people on board that investigates space or another world. Exploring space →
Star: A huge ball of hot gas that gives out its own light and heat. The Universe and our Solar System →
Subscript: A small number after a symbol or bracket that tells you how many atoms or groups are represented. The periodic table and formulae →
Surface gravity: The gravitational force on each kilogram near a planet’s or moon’s surface. Planets, seasons and the Moon →
Surroundings: The solution, container, air and other things around the reacting substances. Energy changes in reactions →
Sustainable production: Producing what people need while protecting resources and ecosystems for the future. Biodiversity and food production →
Technology assessment: Explaining how a technology works and judging its benefits and drawbacks. Technology and electricity choices →
Temperature: A measure of how hot or cold something is, usually given in degrees Celsius (°C). Heat, light and sound →
Testable question: A question that can be answered using observations or measurements. Planning an investigation →
Tissue: A group of cells working together to do a particular job. Cells and living things →
Trade-off: A choice that improves one thing but makes another worse. Technology and electricity choices →
Trade-off: A choice where gaining one benefit means giving up another. Materials and sustainability →
Transfer: Energy moving from one place to another, such as from a battery to a lamp. Energy and conservation →
Transpiration: The loss of water vapour from a plant, mainly through tiny pores in its leaves. The water and carbon cycles →
Uncertainty: A limit to how exactly we can measure something or how confidently we can explain it. Models, evidence and communication →
Variation: Differences between individuals of the same species. Inheritance and variation →
Vein: A blood vessel that carries blood towards the heart. The heart and circulation →
Velocity: Speed in a stated direction, such as 5 m/s east. Motion, speed and acceleration →
Ventilation: Movement of air into and out of the lungs. Breathing and gas exchange →
Villus: A tiny finger-like projection in the small intestine that provides surface area for absorption. Digestion and nutrition →
Volume: The space an object or substance takes up. It can be measured in cm³ or mL; 1 mL = 1 cm³. Measurement and density →
Weather: Conditions such as temperature, rain and wind at a particular place and time. Energy resources and climate →
Weight: The force of gravity on an object. Weight = mass × gravitational field strength. Forces, weight and pressure →