Learning science words that start with O can help students build a stronger vocabulary. These terms appear in physics, earth studies, biology, and environmental topics, so they are very helpful in learning.
This article explains important science words starting with O in different categories. You will find physical science, earth science, life science, environmental science, general science, and computer science terms. It also includes easy vocabulary for kids and grade-wise lists with clear meanings, making science learning simple and fun.
Physical Science Words That Start With O
Physical science encompasses physics and chemistry, studying matter, energy, and their interactions.
| Word | Meaning |
| Orbit | The curved path of an object around a star, planet, or moon |
| Oxygen | A chemical element essential for respiration and combustion |
| Oscillation | Repetitive back and forth movement around a central point |
| Optics | The branch of physics dealing with light and vision |
| Oxidation | A chemical reaction involving the loss of electrons |
| Ohm | The unit of electrical resistance |
| Osmosis | Movement of solvent through a semipermeable membrane |
| Octane | A hydrocarbon compound found in gasoline |
| Orbital | A region around an atom’s nucleus where electrons are found |
| Ozone | A molecule consisting of three oxygen atoms |
| Ounce | A unit of weight in the imperial system |
| Opaque | Not allowing light to pass through |
| Omnidirectional | Radiating or receiving equally in all directions |
| Ohmmeter | An instrument for measuring electrical resistance |
| Oxide | A compound formed by oxygen with another element |
| Oscillator | A device that produces regular vibrations or waves |
| Overpressure | Pressure exceeding normal atmospheric pressure |
| Optometer | An instrument for measuring the refractive power of the eye |
| Orthogonal | At right angles; perpendicular |
| Octave | An interval spanning eight notes in music or doubling of frequency |
Earth Science Words That Start With O
Earth science explores our planet’s physical structure, atmosphere, and natural phenomena.
| Word | Meaning |
| Oceanic | Relating to or characteristic of the ocean |
| Outcrop | A visible exposure of bedrock or ancient rock on the surface |
| Orogeny | The process of mountain formation through tectonic forces |
| Obsidian | A naturally occurring volcanic glass formed from rapidly cooling lava |
| Ore | Rock or mineral from which valuable metals can be extracted |
| Overburden | Soil and rock overlying a mineral deposit |
| Oxbow | A U-shaped lake formed when a river meander is cut off |
| Oceanography | The scientific study of the ocean |
| Orographic | Related to mountains, especially regarding precipitation |
| Olivine | A green silicate mineral found in igneous rocks |
| Ooze | Soft mud or slime, especially on a riverbed or seabed |
| Oligocene | A geological epoch from 34 to 23 million years ago |
| Ordovician | A geological period from 485 to 444 million years ago |
| Occluded Front | A weather front where a cold front overtakes a warm front |
| Outgassing | The release of gases from rocks or the Earth’s interior |
| Oxisol | A type of highly weathered tropical soil |
| Orthoclase | A common feldspar mineral found in granite |
| Ooid | A small rounded sedimentary grain with concentric layers |
| Outcropping | The process of rock becoming exposed at the surface |
| Overturning | Vertical circulation of water in oceans or lakes |
Life Science Words That Start With O
Life science focuses on living organisms, their structure, function, and interactions.
| Word | Meaning |
| Organism | Any individual living thing, from bacteria to humans |
| Organ | A group of tissues working together to perform a function |
| Ovary | The female reproductive organ that produces eggs |
| Omnivore | An organism that eats both plants and animals |
| Ovulation | The release of an egg from the ovary |
| Organelle | A specialized structure within a cell |
| Osmotic | Relating to the movement of water across membranes |
| Olfactory | Relating to the sense of smell |
| Oviparous | Reproducing by laying eggs |
| Offspring | The young produced by an organism |
| Operon | A cluster of genes regulated together in bacteria |
| Osteoblast | A cell that forms bone tissue |
| Osteocyte | A mature bone cell |
| Ovule | The structure in plants that develops into a seed |
| Oxidative | Involving or requiring oxygen |
| Ontogeny | The development of an individual organism |
| Oocyte | An immature egg cell |
| Operon | A functioning unit of DNA containing genes |
| Osmoregulation | The control of water and salt balance in organisms |
| Organogenesis | The formation and development of organs |
Environmental Science Words That Start With O
Environmental science studies the interactions between physical, chemical, and biological components of the environment.
| Word | Meaning |
| Ozone Layer | The region of Earth’s atmosphere that absorbs ultraviolet radiation |
| Organic | Derived from living matter or containing carbon compounds |
| Overpopulation | Excessive population density causing environmental strain |
| Overfishing | Catching fish faster than they can reproduce |
| Oil Spill | Release of liquid petroleum into the environment |
| Overconsumption | Using resources faster than they can be replenished |
| Oxidizer | A substance that produces oxygen for combustion |
| Outfall | The point where wastewater is discharged into the environment |
| Offgas | To release gases from materials into the air |
| Overgrazing | Excessive grazing that damages vegetation |
| Overwinter | To survive or spend the winter season |
| Oligotrophic | Describing water bodies with low nutrient levels |
| Organic Farming | Agriculture without synthetic pesticides or fertilizers |
| Oil Refinery | A facility that processes crude oil |
| Overexploitation | Using natural resources faster than they regenerate |
| Ozonation | Treatment of water or air with ozone |
| Offset | Compensation for carbon emissions through positive actions |
| Organic Matter | Material derived from dead plants and animals |
| Overstory | The uppermost canopy layer in a forest |
| Oxygen Depletion | Reduction of dissolved oxygen in water |
General Science Words That Start With O
These are fundamental science terms used across multiple disciplines.
| Word | Meaning |
| Observation | The act of noting and recording facts or occurrences |
| Objective | Based on observable phenomena; unbiased |
| Odor | A smell, especially an unpleasant one |
| Olfaction | The sense of smell |
| Omnipresent | Present everywhere simultaneously |
| Ova | Plural form of ovum; egg cells |
| Ovum | A mature female reproductive cell |
| Optimize | To make the best or most effective use of something |
| Outage | A period when a system is not operational |
| Outbreak | A sudden occurrence or increase of disease |
| Output | The amount of energy or product produced |
| Overdose | An excessive and dangerous dose of a drug |
| Overtone | A higher frequency component of a sound |
| Outlier | A data point that differs significantly from others |
| Outcome | The result or consequence of an action or process |
| Overhead | The indirect costs or resources required |
| Overload | An excessive amount beyond capacity |
| Overshoot | To exceed a target or intended limit |
| Oxygenate | To supply or treat with oxygen |
| Obsolete | No longer in use or outdated |
Computer Science Words That Start With O
Computer science vocabulary is essential for understanding technology and programming.
| Word | Meaning |
| Operating System | Software that manages computer hardware and software resources |
| Object | An instance of a class in object-oriented programming |
| Output | Data produced by a computer or program |
| Operator | A symbol representing a mathematical or logical operation |
| Overflow | When a calculation produces a result too large to store |
| Overwrite | To replace existing data with new data |
| Offline | Not connected to a network or the internet |
| Online | Connected to a network or the internet |
| Operand | A value on which an operation is performed |
| Optimization | Improving code efficiency or performance |
| Open Source | Software with publicly accessible source code |
| Override | To replace or supersede default behavior |
| Octal | A base-8 number system |
| Offset | The distance from a starting point in memory |
| Obfuscation | Making code difficult to understand |
| Object-Oriented | Programming paradigm based on objects and classes |
| Outbox | A folder for messages waiting to be sent |
| Overlay | To place one element on top of another |
| OAuth | An open standard for access delegation |
| Octet | A unit of digital information consisting of eight bits |
Science Words That Start With O With Meaning
Here’s a comprehensive list of important science terms with detailed meanings.
| Word | Meaning |
| Observatory | A facility equipped for observing astronomical phenomena |
| Obtuse | An angle greater than 90 degrees but less than 180 degrees |
| Occipital | Relating to the back part of the head or skull |
| Oceanology | The scientific study of the sea and marine life |
| Octagon | A polygon with eight sides and eight angles |
| Ocular | Relating to the eyes or vision |
| Odometer | An instrument for measuring distance traveled |
| Omniscient | Having complete or unlimited knowledge |
| Oncology | The branch of medicine dealing with cancer |
| Opacity | The quality of being impenetrable to light |
| Operon Model | A genetic regulatory system in prokaryotes |
| Opposable | Capable of being placed against other digits |
| Optical | Relating to sight or vision |
| Optician | A professional who makes or sells eyeglasses |
| Optimum | The most favorable conditions for growth or success |
| Oral | Relating to the mouth |
| Ordinate | The vertical coordinate in a coordinate system |
| Organics | Chemistry branch dealing with carbon compounds |
| Orientation | The relative position or direction of something |
| Orthopedic | Relating to the correction of bone deformities |
Science Words That Start With O For Kids
Simple science words appropriate for young learners.
| Word | Meaning |
| Ocean | A very large body of salt water |
| Oil | A slippery liquid that doesn’t mix with water |
| Orange | A color or a citrus fruit rich in vitamin C |
| Orbit | The path a planet takes around the sun |
| Otter | A furry water animal that eats fish |
| Owl | A nocturnal bird with large eyes |
| Oxygen | The gas we breathe to stay alive |
| Oyster | A shellfish that lives in the ocean |
| Octopus | A sea creature with eight arms |
| Oval | An egg-shaped or elongated circle |
| Outside | The outer part or external area |
| Oven | A heated chamber for cooking food |
| Ostrich | The largest bird that cannot fly |
| Oak | A large tree that produces acorns |
| Oatmeal | A nutritious breakfast cereal made from oats |
| Observe | To watch carefully |
| Odor | A smell or scent |
| Offspring | Baby animals or children |
| Orbit | Going around something in a circle |
| Organs | Body parts that do special jobs |
Science Words That Start With O 5th Grade
Age-appropriate science vocabulary for fifth-grade students.
| Word | Meaning |
| Orbit | The path one celestial body takes around another |
| Organism | Any living thing such as plants, animals, or bacteria |
| Organ System | A group of organs working together |
| Oxygen | Element essential for respiration in most living things |
| Omnivore | An animal that eats both plants and meat |
| Opaque | Material that blocks light from passing through |
| Ovary | The part of a flower that contains seeds |
| Ovule | The structure that becomes a seed after fertilization |
| Observation | Using senses to gather information |
| Offspring | The young produced by living organisms |
| Outer Core | The liquid layer of Earth beneath the mantle |
| Ozone | A gas in Earth’s atmosphere that blocks UV rays |
| Ore | Rock containing valuable minerals or metals |
| Oxidation | A chemical change involving oxygen |
| Optical Illusion | An image that tricks the eye |
| Orbit Period | The time it takes to complete one orbit |
| Osmosis | Movement of water through a membrane |
| Overpopulation | Too many organisms in an area |
| Ocean Current | A continuous flow of water in the ocean |
| Outcrop | Rock visible at Earth’s surface |
Science Words That Start With O 6th Grade
Middle school science terms for sixth graders.
| Word | Meaning |
| Orbit | The gravitational curved path of an object in space |
| Organelle | A specialized structure inside a cell |
| Organism | A complete living system capable of reproduction |
| Osmosis | Diffusion of water across a selectively permeable membrane |
| Oxidation | A reaction where a substance loses electrons |
| Optics | The study of light and its behavior |
| Ocean Trench | The deepest parts of the ocean floor |
| Ozone Layer | Atmospheric region that absorbs harmful UV radiation |
| Omnivore | An organism that consumes both plants and animals |
| Ovulation | The release of an egg from the ovary |
| Organ | A structure composed of tissues performing specific functions |
| Orbital | The region where electrons are likely found |
| Ohm’s Law | The relationship between voltage, current, and resistance |
| Outcrop | Exposed bedrock at Earth’s surface |
| Offspring | Descendants or young of an organism |
| Ovary | Female reproductive organ producing eggs |
| Organic Compound | A molecule containing carbon and hydrogen |
| Oscillation | Repeated back-and-forth motion |
| Ore Deposit | A concentration of minerals in rock |
| Oxygen Cycle | The movement of oxygen through ecosystems |
Science Words That Start With O 7th Grade
Advanced middle school science vocabulary.
| Word | Meaning |
| Orbit | The elliptical path determined by gravitational forces |
| Organelle | Membrane-bound structures performing cellular functions |
| Osmotic Pressure | Pressure required to prevent water movement across a membrane |
| Oxidation-Reduction | A reaction involving transfer of electrons between substances |
| Orogeny | Mountain-building process through tectonic plate collision |
| Oscillator | A system producing repetitive variations over time |
| Optical Fiber | A flexible glass strand transmitting light signals |
| Ozone Depletion | Reduction of ozone in the stratosphere |
| Omnidirectional | Transmitting or receiving signals in all directions |
| Ovum | A mature female gamete or egg cell |
| Orbital Velocity | Speed required to maintain orbit around a body |
| Organism Kingdom | Major classification group of living things |
| Obsidian | Volcanic glass formed from rapidly cooled lava |
| Ohmmeter | Device measuring electrical resistance |
| Oceanography | Scientific study of ocean properties and phenomena |
| Operon | Group of genes regulated together in prokaryotes |
| Ordovician Period | Geological time period 485-444 million years ago |
| Olfactory Nerve | Cranial nerve responsible for sense of smell |
| Oviparity | Reproduction by laying eggs that develop externally |
| Orthogonal | Perpendicular or at right angles |
Science Words That Start With O 8th Grade
High-level middle school science terminology.
| Word | Meaning |
| Orbital Mechanics | Physics governing motion of objects in space |
| Organogenesis | The formation and development of organs during embryonic development |
| Osmolarity | Concentration of osmotically active particles in solution |
| Oxidative Phosphorylation | ATP production using energy from electron transfer |
| Orographic Lift | Air rising due to terrain elevation changes |
| Oscilloscope | Electronic device displaying varying electrical signals |
| Optical Spectrum | The range of electromagnetic waves visible to humans |
| Ozone Chemistry | Chemical reactions involving ozone formation and destruction |
| Oncogene | A gene that can transform normal cells into cancer cells |
| Ovule Development | Formation of female reproductive structures in plants |
| Orbital Hybridization | Mixing of atomic orbitals to form new hybrid orbitals |
| Oligotrophic Lake | Water body with low nutrient and high oxygen levels |
| Oxbow Lake | Crescent-shaped lake formed from river meander cutoff |
| Ohm’s Law Application | Using V=IR in electrical circuit analysis |
| Oceanic Crust | Dense basaltic layer forming ocean basin floors |
| Osteogenesis | The process of bone tissue formation |
| Organophosphate | Chemical compounds containing phosphorus used as pesticides |
| Orthoclase Feldspar | Common mineral in granite and metamorphic rocks |
| Ovipositon | The act of laying or depositing eggs |
| Oxidation State | The degree of oxidation of an atom in a compound |
Conclusion
This comprehensive guide provides science vocabulary words starting with “O” across multiple disciplines and grade levels. These terms form the foundation for understanding scientific concepts from elementary through middle school.
Regular review and practical application of these words will enhance scientific literacy and academic performance. Students should practice using these terms in context to fully grasp their meanings and applications in various scientific fields.
