Science Words That Start With O: Key Terms Explained

Discover a comprehensive list of science-related words that start with the letter ‘O’ to enhance your vocabulary and understanding of scientific concepts.

  1. Observation- The act of noting and recording something with instruments.
  2. Orbit- The gravitationally curved trajectory of an object around a point in space.
  3. Osmosis- The process of gradual or unconscious assimilation of ideas, knowledge, etc.
  4. Oxidation- The process or result of oxidizing or being oxidized, especially in a chemical reaction.
  5. Ozone- A form of oxygen with three atoms in its molecule, O₃, found in the Earth’s stratosphere.
  6. Organism- An individual living thing that can react, reproduce, and grow.
  7. Oscillation- Movement back and forth at a regular speed.
  8. Omnivore- An animal or person that eats food of both plant and animal origin.
  9. Oncology- The study and treatment of tumors.
  10. Ornithology- The scientific study of birds.
  11. Opal- A hydrated amorphous form of silica, a mineral.
  12. Orbital- A region in an atom where there is a high probability of finding electrons.
  13. Ostium- An opening into a vessel or cavity of the body.
  14. Ocular- Related to the eye or vision.
  15. Optics- The scientific study of sight and the behavior of light.
  16. Ovum- A mature female reproductive cell.
  17. Osteology- The study of the structure and function of the skeleton and bony structures.
  18. Oxidant- A substance that has the ability to oxidize other substances.
  19. Osmoregulation- The control of water and salt concentrations in an organism.
  20. Organelles- Specialized structures within a living cell.
  21. Orogeny- The process of mountain formation, especially by folding of the earth’s crust.
  22. Osteoblast- A cell that secretes the matrix for bone formation.
  23. Ovary- The female reproductive organ in which ova or eggs are produced.
  24. Ozone Layer- A layer in the earth’s stratosphere that absorbs most of the sun’s UV radiation.
  25. Orthophosphate- A salt or ester of orthophosphoric acid.
  26. Obligate- Necessary or required (especially related to mutual relationships in organisms).
  27. Oscilloscope- An instrument for measuring and displaying alternating current.
  28. Orbitomeatal- Pertaining to the orbit (eye socket) and the external auditory meatus (ear canal).
  29. Osteoclast- A large multinucleated bone cell which absorbs bone tissue during growth and healing.
  30. Organogenesis- The formation and development of organs in living organisms.
  31. Ototoxic- Having a toxic effect on the ear or its nerve supply.
  32. Orbital Plane- The geometric plane in which the orbit lies.
  33. Oxytocin- A hormone that causes contraction of the uterus and milk ejection in mammals.
  34. Oscillator- An electronic device or circuit that produces a periodic oscillating electronic signal.
  35. Obsidian- A natural volcanic glass.
  36. Orthopnea- Shortness of breath that occurs when lying flat.
  37. Oncogene- A gene that has the potential to cause cancer.
  38. Orthophosphate- A phosphate containing one phosphate group.
  39. Oxygenation- The process of supplying, treating, or mixing with oxygen.
  40. Osteogenesis- The process of bone formation.
  41. Oogenesis- The process by which the female gametes, or ova, are created.
  42. Ochre- A naturally occurring pigment containing hydrated iron oxide.
  43. Osteoporosis- A medical condition in which the bones become brittle and fragile.
  44. Olfaction- The sense of smell.
  45. Outlier- A data point that differs significantly from other observations.
  46. Overtones- Higher frequencies present in a sound than the fundamental frequency.
  47. Optoelectronics- The study and application of electronic devices that source, detect, and control light.
  48. Octane- A hydrocarbon of the alkane series, used in fuel mixtures.
  49. Optical Fibre- A thin fiber of glass or plastic that transmits light.
  50. Oxytocinase- An enzyme that degrades oxytocin, a hormone involved in childbirth and lactation.
  51. Oolong- A traditional Chinese tea.
  52. Ovulate- To discharge an ovum from the ovary.
  53. Orthoscope- An instrument for viewing the interior of the eye.
  54. Oligotrophic- Environments that offer low levels of nutrients.
  55. Organic Chemistry- The chemistry of carbon compounds.
  56. Osmometer- An instrument for measuring osmotic pressure of a solution.
  57. Oenology- The study of wines.
  58. Orogacin- A non-T cell superantigen.
  59. Orthoclase- A common alkali feldspar mineral.
  60. Orthodromicity- The property of following the shortest path between two points.
  61. Overnutrition- Excessive intake of nutrients.
  62. Olfactory Bulb- The brain structure responsible for the sense of smell.
  63. Ontogeny- The development or course of development of an individual organism.
  64. Oomycetes- A group of fungus-like eukaryotic microorganisms.
  65. Oxidative Stress- Damage to the body caused by free radicals.
  66. Orthopoxvirus- A genus of viruses that includes the pathogens of smallpox.
  67. Ozone Hole- A thinning region of the ozone layer.
  68. Oxyacids- Acids that contain oxygen.
  69. Operational Amplifier- An integrated circuit that amplifies voltage.
  70. Osmolality- The concentration of a solution expressed as osmoles of solute per kilogram of solvent.
  71. Optogenetics- A technique in neuroscience to control cells within living tissue.
  72. Orthostatic Hypotension- A form of low blood pressure that happens when standing up.
  73. Oscillograph- An instrument for recording oscillations.
  74. Oleic acid- A fatty acid that occurs naturally in various animal and vegetable fats.
  75. Oxazole- A five-membered ring compound containing oxygen and nitrogen.
  76. Ozonolysis- A reaction in which ozone breaks down organic compounds.
  77. Opsin- A protein in the photoreceptor cells of the retina.
  78. Oxymoron- A figure of speech in which apparently contradictory terms appear in conjunction.
  79. Oleophilic- Having a strong affinity for oils.
  80. Otolaryngology- The study of diseases of the ear, nose, and throat.
  81. Ophiolite- Section of the Earth’s oceanic crust and upper mantle that has been uplifted and exposed above sea level.
  82. Osteomyelitis- Infection of bone tissue.
  83. Observatory- A place equipped for observing astronomical phenomena.
  84. Octoploid- Organism with eight sets of chromosomes.
  85. Oscillatory Motion- Repeated back and forth movement around a central point.
  86. Orthogenesis- Hypothetical evolutionary development in a predictable direction.
  87. Overdominance- A condition in genetics where the heterozygote has a higher fitness than either homozygote.
  88. Oxidative Phosphorylation- The metabolic pathway in which cells use enzymes to oxidize nutrients.
  89. Orthogonal- Of or involving right angles.
  90. Osteoarthritis- A chronic condition characterized by the breakdown of the joint’s cartilage.
  91. Oblique Muscle- A muscle neither parallel nor perpendicular to the long axis of a body or limb.
  92. Oxyfuel- Fuel that uses oxygen for combustion.
  93. Oscillopsia- A condition where the patient perceives the world as swinging.
  94. Obturator- A prosthesis that closes an opening in the body.
  95. Occlusion- The blockage or closing of a blood vessel or hollow organ.
  96. Optometer- An instrument for measuring the refractive power of the eye.
  97. Onychomycosis- Fungal infection of the nails.
  98. Ovolo- A rounded convex molding, quarter-round.
  99. Otorhinolaryngology- The study of diseases of the ear, nose, and throat.
  100. Omphalos- The navel or central point.

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