238 Nouns That Start with O [with Definitions and Examples]

To make one’s conversations and writings meticulous, professional and captivating, one should have a vast encyclopedia of nouns at one’s command, especially nouns that start with O. Memorizing a number of nouns beginning with O can prove to be a very fruitful step in achieving that goal. Nouns are important because they refer to places, objects and people and the more sophisticated abstract concepts. Without nouns, you will be left with verbs, adjectives and adverbs. The lack of nouns will eradicate any subject or object from your sentence which is as good as communication essentially nothing.

If you, as a reader, get hold of as many nouns starting with O as possible, you can build for yourself an impressive rapport among other speakers and writers. A list of nouns that start with O is provided in this article for your convenience. Now let’s go through the various categories of nouns provided in this article that also contains nouns that start with O to describe a person, place, and other abstract things. Learning nouns that start with O will not just help you in building your vocabulary but will also make you stand apart from the rest.

Nouns That Start with O You Always Use

There are lots of nouns starting with O that we use on a regular basis in our writings and day-to-day oral communications. Nouns that start with O that one uses regularly are listed below.

1. Office

  • Definition: a room, set of rooms, or building used as a place for commercial, professional, or bureaucratic work
  • Synonyms: workplace, workroom
  • Example: I don’t leave the office until eight o’clock last night.

2. Orange

  • Definition: a round sweet fruit that has a thick orange skin and an orange center divided into many parts
  • Synonyms: citrus-fruits, tangerine
  • Example: Vitamin C is found in oranges and other citrus fruit.

3. Option

  • Definition: one thing that can be chosen from a set of possibilities
  • Synonyms: choice, preference, alternative
  • Example: The best option would be to cancel the trip altogether.

4. Object

  • Definition: a thing that you can see or touch but that is not usually a living animal, plant, or person
  • Synonyms: thing, item, body
  • Example: A new baby will automatically curl its fingers round any object it touches.

5. Observation

  • Definition: the act of observing something or someone
  • Synonyms: examination, consideration, investigation
  • Example: The police are keeping the suspect under observation.

6. Oxygen

  • Definition: a colorless, odorless reactive gas; the life-supporting component of the air
  • Synonyms: gas, air, oxygenation
  • Example: Oxygen is in high demand these days because of Covid-19.

7. Oil

  • Definition: a viscous liquid derived from petroleum, especially for use as a fuel or lubricant
  • Synonyms: lubricant, fuel, petrol
  • Example: Oil does not mix with water.

8. Omelet

  • Definition: a dish of beaten eggs cooked in a frying pan and served plain or with a savory or sweet topping or filling
  • Synonyms: scrambled-egg, frittata
  • Example: I’ll have an omelet with cheese on the side, please.

9.  Outside

  • Definition: the outer part or side of something
  • Synonyms: exterior, surface
  • Example: The outside of the house needs painting.

10. Onion

  • Definition: a swollen edible bulb used as a vegetable, and composed of several concentric layers
  • Synonyms: shallots, allium cepa,
  • Example: Cook the onion in the oil until lightly colored.

Nouns That Start with O You Usually Use

With nouns, sentences are given more clarity as listeners would know what is the object or thing being mentioned and what is happening to that particular object or thing. Following is a list of nouns starting with O that we usually use in our daily life routine.

1. Origin

  • Definition: the point or place where something begins, or arises
  • Synonyms: beginning, start, origination
  • Example: There are many theories about the origin of life.

2. Opinion

  • Definition: a thought or belief about something or someone
  • Synonyms: viewpoint, angle, judgement
  • Example: What’s your opinion about this matter?

3. Oven

  • Definition: an enclosed compartment, usually part of a cooker, for cooking and heating food
  • Synonyms: stove, microwave, roaster
  • Example: She completely forgot the cake in the oven.

4. Operation

  • Definition: an act of surgery performed on a patient
  • Synonyms: surgery, incision, resection
  • Example: I’ve never felt better since my bypass operation.

5. Order

  • Definition: a request to make, supply, or deliver food or goods
  • Synonyms: command, request, instruction
  • Example: “Can I take your order now?” said the waiter.

6. Owner

  • Definition: a person who owns something
  • Synonyms: possessor, holder
  • Example: He and his sister are the owners of the restaurant.

7. Outfit

  • Definition: a set of clothes worn for a particular occasion or activity
  • Synonyms: costume, uniform, suit
  • Example: I’m going to wear my vampire outfit for Halloween.

8. Ornament

  • Definition: a thing used or serving to make something look more attractive but usually having no practical purpose
  • Synonyms: trinket, accessory, bibelot
  • Example: They spent decades collecting these colorful ornaments.

9. Officer

  • Definition: a member of the police force
  • Synonyms: agent, chief, deputy
  • Example: Two officers responded to the call at 282 Main Street.

10. Odor

  • Definition: a particular smell, especially a bad one
  • Synonyms: smell, aroma, stench
  • Example: The odor she had smelled earlier hung in the air.

Nouns That Start with O You Often Use

It’s difficult to write a sentence that does not include at least one noun. Following is a list of nouns starting with O that we often make use of.

1. Organization

  • Definition: a group of people who work together in an organized way for a shared purpose
  • Synonyms: company, firm, corporation
  • Example: The article was about the international aid organizations.

2. Oath

  • Definition: a serious promise that you will tell the truth or that you will do what you have said
  • Synonyms: pledge, vow, promise,
  • Example: Presidents take an oath to uphold the Constitution.

3. Offer

  • Definition: an expression of readiness to do or give something if desired
  • Synonyms: proposal, suggestion, proposition
  • Example: One day I’ll take you up on that offer.

4. Ounce

  • Definition: a very small amount of something
  • Synonyms: scrap, bit, iota
  • Example: Robyn summoned up every ounce of strength.

5. Objection

  • Definition: an expression or feeling of disapproval or opposition; a reason for disagreeing
  • Synonyms: complaint, grievance, protestation
  • Example: They have raised no objections to the latest plans.

6. Occasion

  • Definition: a particular time, especially when something happens or has happened
  • Synonyms: moment, event, circumstance
  • Example: We met on several occasions to discuss the issue.

7. Operator

  • Definition: someone who is skilled at dealing with people and getting what he or she wants from a situation
  • Synonyms: machinist, worker, dealer, arranger
  • Example: The tour operator will arrange transport and plan your itinerary.

8. Obesity

  • Definition: the condition of being very fat or overweight
  • Synonyms: fatness, stoutness, corpulence
  • Example: His obesity puts him at risk for major health problems.

9. Opening

  • Definition: a space or gap that allows passage or access
  • Synonyms: hole, aperture, gap
  • Example: An opening in the roof would get rid of the smoke.

10. Omen

  • Definition: something that is considered to be a sign of how a future event will take place
  • Synonyms: sign, foreshadowing, symbol
  • Example: Many people believe that a broken mirror is an omen of bad luck.

Nouns That Start with O You Sometimes Use

Nouns are very important for language development. They also enhance people’s overall expressive language. These are some of the nouns beginning with O that are not used on a regular basis in our daily life routine.

1. Obligation

  • Definition: an act or course of action to which a person is morally or legally bound
  • Synonyms: duty, commitment, responsibility
  • Example: I have an obligation to look after her.

2. Obstacle

  • Definition: a thing that blocks one’s way or prevents or hinders progress
  • Synonyms: The major obstacle to achieving that goal is money
  • Example: barrier, hurdle

3. Obsession

  • Definition: the state of being obsessed with someone or something
  • Synonyms: fixation, compulsion, fascination
  • Example: The kids have an obsession with computer games.

4. Offspring

  • Definition: children or young of a particular parent or progenitor
  • Synonyms: baby, kid, pup, children
  • Example: Tom’s sister came over on Saturday with all her offspring.

5. Organ

  • Definition: a part of the body of an animal or plant that performs a particular job
  • Synonyms: unit, part, structure
  • Example: He sustained injuries to his arms, legs and several internal organs.

6. Oration

  • Definition: a formal public speech about a serious subject
  • Synonyms: speech, address, lecture
  • Example: He asked for no funeral oration.

7. Organism

  • Definition: an individual animal, plant, or single-celled life form
  • Synonyms: being, creature, animal
  • Example: Amoebae and bacteria are single-celled organisms.

8. Oatmeal

  • Definition: meal made from ground oats, used in porridge or oatcakes
  • Synonyms: cereal, porridge
  • Example: I switched back to oatmeal for four days.

9. Oppression

  • Definition: the state of being subject to oppressive treatment
  • Synonyms: persecution, abuse, maltreatment
  • Example: Every human being has the right to freedom from oppression.

10. Orphanage

  • Definition: a home for children whose parents are dead or unable to care for them
  • Synonyms: asylum, shelter, foundation
  • Example: He donated 1,000 dollars to an orphanage.

Nouns That Start with O You Occasionally Use

Most of the noun words that start with O might be pretty commonly used, but there are some that are only used at some specific occasions. Following is a list of such nouns.

1. Oaf

  • Definition: a man who is rough or clumsy and unintelligent
  • Synonyms: clown, gawk, hulk
  • Example: They are just big, clumsy oafs.

2. Omnibus

  • Definition: a usually automotive public vehicle designed to carry a large number of passengers
  • Synonyms: bus, vehicle, tram
  • Example: In our neighborhood, most of the children ride an omnibus to school each day.

3. Onslaught

  • Definition: a fierce or destructive attack
  • Synonyms: charge, assault, attack
  • Example: It is unlikely that his forces could withstand an enemy onslaught for very long.

4. Opiate

  • Definition: a drug that contains opium, especially one that causes sleep
  • Synonyms: drug, narcotic, sedative
  • Example: One woman suffered such severe pain she had to take opiates to control it.

5. Optician

  • Definition: a person qualified to prescribe and dispense glasses and contact lenses, and to detect eye diseases
  • Synonyms: ophthalmologist, occulist
  • Example: Her youngest daughter is an optician.

6. Orgy

  • Definition: a period when there is too much of something, usually a bad or harmful activity
  • Synonyms: debauch, carouse, bacchanalia
  • Example: The protest degenerated into an orgy of looting and shooting.

7. Orient

  • Definition: the countries of East and Southeast Asia
  • Synonyms: east, exotic, muddle
  • Example: Is the Orient too foreign for you?

8. Ordnance

  • Definition: military supplies, especially weapons and bombs
  • Synonyms: guns, cannon, artillery
  • Example: The gun was a brand new piece of ordnance.

9. Osmosis

  • Definition: a spontaneous diffusion of water or other solvents through a semipermeable membrane
  • Synonyms: diffusion, infiltration
  • Example: Fluid flows back into the tiny blood vessels by osmosis.

10. Omnipotence

  • Definition: unlimited power and the ability to do anything
  • Synonyms: supremacy, pre-eminence
  • Example: America had illusions of omnipotence in the 1950s.

Nouns That Start with O You Seldom Use

While going through a written piece or while listening to a person talking, you often come across nouns that you haven’t heard of a lot. Below is a list of noun words that start with the letter O that are seldom used.

1. Obelisk

  • Definition: a tapering stone pillar, typically having a square or rectangular cross section, set up as a monument or landmark
  • Synonyms: pillar, monument, memorial
  • Example: Each obelisk listed the members of an immortal household and their offspring.

2. Ogre

  • Definition: a fierce and frightening person
  • Synonyms: monster, bogeyman, devil
  • Example: Some of my teachers were real ogres.

3. Oligarchy

  • Definition: government by a small group of powerful people
  • Synonyms: authoritarianism, autocracy, totalitarianism
  • Example: Their nation is an oligarchy.

4. Onyx

  • Definition: a valuable stone that is used in jewelry, with white, black, grey, and other colored stripes
  • Synonyms: stone, mineral, slab
  • Example: Has my story of that pearl and onyx been lost on you?

5. Opus

  • Definition: any work of art
  • Synonyms: composition, work, piece
  • Example: He showed us his latest opus, a truly magnificent painting of a vase of flowers.

6. Ornithology

  • Definition: the study of birds
  • Synonyms: science, zoology, research
  • Example: He found his vocation in ornithology.

7. Overalls

  • Definition: a loose-fitting coat or one-piece garment worn over ordinary clothes for protection against dirt or heavy wear
  • Synonyms: dungarees, outfit
  • Example: She put on some overalls and got out a tin of paint.

8. Osteopathy

  • Definition: the treatment of injuries to bones and muscles using pressure and movement
  • Synonyms: ministration, surgery
  • Example: Osteopathy involves massage and manipulation of the bones and joints.

9. Oxymoron

  • Definition: a figure of speech in which apparently contradictory terms appear in conjunction
  • Synonyms: opposites, juxtaposition
  • Example: The genre of ‘historical fiction’ is an oxymoron to begin with.

10. Onomatopoeia

  • Definition: the act of creating or using words that include sounds that are similar to the noises the words refer to
  • Synonyms: echo, repetition, imitation
  • Example: When asked to point out the onomatopoeia in the sentence describing a bird, I pointed to “chirp”.

Nouns That Start with O You Rarely Use

There are some O-nouns that are rarely seen or heard in both writing and communication. When a reader gets to know about them he is flabbergasted that such nouns even exist. Below are some of those nouns.

1. Obeisance

  • Definition: a gesture expressing deferential respect, such as a bow or curtsy
  • Synonyms: salutation, curtesy, bob
  • Example: She made a deep obeisance.

2. Opprobrium

  • Definition: harsh criticism or censure
  • Synonyms: vituperation, criticism, censure
  • Example: International opprobrium has been heaped on the country following its attack on its neighbors.

3. Oblation

  • Definition: something that is offered as a religious sacrifice
  • Synonyms: offering, sacrifice, libation
  • Example: Incense was used for purification and as an oblation to ancestors.

4. Obliquity

  • Definition: deviation from moral rectitude or sound thinking
  • Synonyms: shift, transgression, turning
  • Example: Barrow’s fade to winter blackness results from cosmic obliquity.

5. Obscurantism

  • Definition: the practice of deliberately preventing the facts or full details of something from becoming known
  • Synonyms: backsliding, backlash, withdrawal
  • Example: Religious prejudice and scientific obscurantism have been closely entangled.

6. Offertory

  • Definition: the offering of the bread and wine at the Eucharist
  • Synonyms: offering, allowance, benefit
  • Example: They donated the money to a collection which was brought up at the offertory.

7. Opulence

  • Definition: the quality of being expensive and luxurious
  • Synonyms: richness, luxury, splendor
  • Example: He says living in such opulence makes him uneasy.

8. Orifice

  • Definition: an opening or hole, especially one in the body, such as the mouth
  • Synonyms: opening, hole, aperture
  • Example: The driver was bleeding from every orifice.

9. Obloquy

  • Definition: very strong public criticism or blame
  • Synonyms: vilification, condemnation, denunciation
  • Example: His controversial essays have brought him much obloquy.

10. Oubliette

  • Definition: a secret dungeon with access only through a trapdoor in its ceiling.
  • Synonyms: dungeon, jail, cell
  • Example: Sarah ends up in an oubliette where she reunites with her husband.

Positive Nouns That Start with O

There are some positive nouns that both carry and spread positivity and also describe your skills, results, and accomplishments. These are some of the positive nouns that start with O that you should have at your disposal.

1. Optimist

  • Definition: a person who tends to be hopeful and confident about the future or the success of something
  • Synonyms: dreamer, hoper, fantast
  • Example: Only an eternal optimist could expect success.

2. Oasis

  • Definition: a fertile spot in a desert, where water is found
  • Synonyms: spring, wellspring
  • Example: They stopped for the night at an oasis.

3. Objective

  • Definition: something that you plan to do or achieve
  • Synonyms: aim, intention, purpose
  • Example: Her prime objective now is simply to stay in power.

4. Occupation

  • Definition: a job or profession
  • Synonyms: work, profession, job
  • Example: Please fill in your name, age, and occupation.

5. Odyssey

  • Definition: a long wandering or voyage usually marked by many changes of fortune
  • Synonyms: adventure, expedition, exploration
  • Example: They departed Texas on a three-year odyssey that took them as far as Japan

6. Obedience

  • Definition: compliance with an order, request, or law or submission to another’s authority
  • Synonyms: acquiescence, compliance
  • Example: Obedience is the first duty of a soldier.

7. Oomph

  • Definition: the quality of being exciting, energetic, or sexually attractive
  • Synonyms: fortitude, stamina, vigor
  • Example: You need to put some oomph into your acting.

8. Opportunity

  • Definition: a time or set of circumstances that makes it possible to do something
  • Synonyms: chance, occasion, moment
  • Example: Please contact us at the earliest opportunity.

9. Ovation

  • Definition: a sustained and enthusiastic show of appreciation from an audience, especially by means of applause
  • Synonyms: applause, clapping, cheering
  • Example: Her performance received a thundering ovation.

10. Overture

  • Definition: a piece of music that is an introduction to a longer piece, especially an opera
  • Synonyms: opening, introduction, prelude
  • Example: The programme opened with the overture to Wagner’s Flying Dutchman.

Nouns That Start with O – Full List (238 words)

  • Oaf
  • Oak
  • Oasis
  • Oath
  • Oathe
  • Oatmeal
  • Obedience
  • Obelisk
  • Obesity
  • Object
  • Objectification
  • Objection
  • Objective
  • Objectivity
  • Objector
  • Obligation
  • Oblige
  • Obliteration
  • Oblivion
  • Oblong
  • Oboist
  • Obscenity
  • Obscurity
  • Observance
  • Observation
  • Observer
  • Obsession
  • Obsidian
  • Obstacle
  • Obstructionist
  • Obverse
  • Ocarina
  • Occasion
  • Occlusion
  • Occupancy
  • Occupant
  • Occupation
  • Occurrence
  • Ocean
  • Oceanography
  • Ocelot
  • Ocher
  • Ochre
  • Octagon
  • Octahedron
  • October
  • Octopus
  • Octoroon
  • Ode
  • Odor
  • Odyssey
  • Oep
  • Offal
  • Offender
  • Offense
  • Offer
  • Offering
  • Offersey
  • Office
  • Officer
  • Official
  • Officialdom
  • Offing
  • Offshoot
  • Offspring
  • Ogre
  • Oil
  • Oilcloth
  • Oiliness
  • Oilseed
  • Ointment
  • Oiticica
  • Oleomargarine
  • Olive
  • Olympian
  • Ome
  • Omelet
  • Omen
  • Omission
  • Ommission
  • Omnipotence
  • Omnipotent
  • Omnivore
  • Oneupmanship
  • Onion
  • Onlooker
  • Onrush
  • Onset
  • Onslaught
  • Oodles
  • Ooh
  • Oomph
  • Ooze
  • Opal
  • Open
  • Opener
  • Opening
  • Openness
  • Opera
  • Operand
  • Operation
  • Operator
  • Operetta
  • Opinion
  • Opium
  • Opponent
  • Opportunism
  • Opportunity
  • Opposite
  • Opposition
  • Oppression
  • Opprobrium
  • Optimality
  • Optimism
  • Optimist
  • Optimization
  • Optimum
  • Option
  • Oracle
  • Oral
  • Orange
  • Oration
  • Orator
  • Oratorio
  • Oratory
  • Orb
  • Orbit
  • Orchard
  • Orchestra
  • Orchestration
  • Orchestrator
  • Ordeal
  • Order
  • Orderly
  • Ordinance
  • Ordinary
  • Ordnance
  • Organ
  • Organdy
  • Organification
  • Organism
  • Organist
  • Organization
  • Organizer
  • Orgasm
  • Orgone
  • Orgy
  • Orientation
  • Origin
  • Original
  • Originality
  • Origination
  • Originator
  • Ornament
  • Ornamental
  • Ornamentation
  • Orphan
  • Orphanage
  • Orthicon
  • Orthodontist
  • Orthography
  • Orthophosphate
  • Oscillation
  • Oscillator
  • Osmium
  • Ossification
  • Ostracism
  • Ostrich
  • Otter
  • Ounce
  • Ouster
  • Outback
  • Outbreak
  • Outburst
  • Outcast
  • Outcome
  • Outcry
  • Outfield
  • Outfielder
  • Outfit
  • Outflow
  • Outgrowth
  • Outhouse
  • Outing
  • Outlaw
  • Outlawry
  • Outlay
  • Outlet
  • Outline
  • Outlook
  • Outpatient
  • Outpost
  • Output
  • Outrage
  • Outreach
  • Outset
  • Outside
  • Outsider
  • Oval
  • Ovation
  • Oven
  • Overall
  • Overcast
  • Overcoat
  • Overestimation
  • Overexploitation
  • Overflow
  • Overhang
  • Overhaul
  • Overhead
  • Overlay
  • Overload
  • Overnight
  • Overpayment
  • Overpopulation
  • Overpressure
  • Overprotection
  • Overrun
  • Overseer
  • Oversight
  • Oversimplification
  • Overthrow
  • Overtime
  • Overture
  • Overweight
  • Owi
  • Owl
  • Owner
  • Ownership
  • Oxalate
  • Oxcart
  • Oxen
  • Oxidation
  • Oxide
  • Oxygen
  • Oxytetracycline
  • Oyster
  • Ozone

Final Thoughts on Nouns That Start with O

It is hoped that you would have learnt something new about the use of nouns while reading this article. There is a never-ending list of nouns and new nouns are being added to it every now and then. By having a large reservoir of nouns at your disposal, you can bring terseness and compactness in your speech and writing that will indirectly build an impressive public self-image for you in the eyes of your audience. There are a number of nouns starting with O that can help you achieve that goal.

By inserting such nouns beginning with O in the phrases, clauses and sentences you utter will bring you great success. This article will also help you in improving your English language skills and clear up any confusion you might have over the use of nouns that start with O in your writings and interactions.

Ps. See also positive words that start with O, adjectives that start with O and verbs that start with O.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button