Words That Start With On: Uncover Unique Vocabulary and Usage Tips

Discover a variety of words starting with the prefix “on” and learn how each one can enhance your vocabulary.

  1. On- Used to indicate position, usually indicating that something is on top of something else.
  2. Once- At one time in the past; formerly.
  3. Only- No one or nothing more besides; solely or exclusively.
  4. Onto- To a position on the surface of something.
  5. Onus- Used to refer to something that is one’s duty or responsibility.
  6. Onyx- A semiprecious stone with bands of color, often used in jewelry or ornamentation.
  7. Onion- A bulbous plant with a strong taste and smell, used in cooking.
  8. Ongoing- Continuing; still in progress.
  9. Onset- The beginning or start, especially of something unwelcome.
  10. Onward- Moving forward or continuing.
  11. One- Referring to a single person or thing.
  12. Onlooker- A non-participating observer; spectator.
  13. Oneiric- Pertaining to dreams.
  14. Onboard- Being on or within a vehicle or vessel.
  15. Online- Controlled by or connected to a computer.
  16. Only- begotten** – Unique, often used in a religious context to indicate a divine relationship.
  17. Onomatopoeia- The formation of a word from a sound associated with what is named.
  18. Oneself- A reflexive form of the pronoun ‘one.’
  19. Onetime- Former, previous.
  20. Onrush- A sudden rapid movement forward.
  21. Onscreen- Appearing on a screen, especially in a cinema or television.
  22. Onsite- Located at the site.
  23. Onstage- Positioned on the stage, usually during a performance.
  24. Onshore- Landward; towards or onto the shore.
  25. Onslaught- A fierce or destructive attack.
  26. Ontology- A branch of metaphysics dealing with the nature of being.
  27. Onward- Directed or moving forward.
  28. Ontogeny- The development of an individual organism or anatomical or behavioral feature from the earliest stage to maturity.
  29. Ontologist- A person who studies or discusses the nature of being, existence, or reality.
  30. Onus- A burden, obligation, or difficult responsibility.
  31. Oncology- The study and treatment of tumors and cancer.
  32. Onlookers- People who watch something (often an event) but do not participate.
  33. Oncoming- Approaching, coming nearer.
  34. Onetime- Done or happening in the past, but not now.
  35. Oneness- The quality or state of being unified or whole.
  36. One- up** – To get an advantage over someone.
  37. On- file** – Recorded or stored in a file.
  38. One- off** – Done, made, or happening only once.
  39. On- dit** – A piece of gossip; a rumor.
  40. Onager- A wild ass of Asia.
  41. Onerous- Involving great effort and difficulty.
  42. On- lap** – Positioned on the lap.
  43. One- sided** – Favoring one side unduly; biased.
  44. Oncologic- Pertaining to the study of tumors and their treatment.
  45. Onnagata- A male performer in traditional Japanese Kabuki theater who specializes in playing female roles.
  46. Oneirism- A mental state involving a dream-like experience while awake.
  47. Onchocerciasis- A disease caused by a parasitic worm, also known as river blindness.
  48. On- core** – Central or core-related.
  49. Oneirist- A person who studies or interprets dreams.
  50. Oneiromancy- Divination through dreams.
  51. Oncogenic- Causing the development of a tumor or tumors.
  52. On- field** – Taking place on the field of play in sports.
  53. Onflow- Flow onward or forward.
  54. On- glaze** – A method of decorating ceramics with enamel applied after the initial firing.
  55. One- upmanship** – The technique or practice of gaining a feeling of superiority over another person.
  56. Oncogene- A gene that in certain circumstances can transform a cell into a tumor cell.
  57. Oncosphere- The larval form of certain parasites.
  58. Oneiricist- A specialist in the interpretation of dreams.
  59. Oncologist- A doctor who specializes in treating cancer.
  60. Onboarded- Enrolled or integrated into an organization.

This list includes diverse words starting with “on,” covering various forms of language including nouns, adjectives, and forms of medical and technical terminology.

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