264 Nouns That Start with O | Best List Ever with Definitions and Examples

by Kimi

This article contains nouns that start with O. Nouns are extremely useful in everyday life, especially if you wish to improve your English skills. You’ll be able to write and speak English like a pro if you have a huge number of nouns starting with O under your sleeve.

It is critical to use sophisticated words, particularly nouns, in order to compose an excellent article or whatever it is that you are attempting to write. These nouns that start with O that we included in this article, can help you develop your vocabulary and write a commendable script. Writing will be a piece of cake for you if you memorize these nouns that start with O.

Because nouns beginning with O are so abundant in the English language, it’s difficult to include all of them in one article. However, I am convinced that there are enough nouns here to let you speak and write English fluently. So, without further ado, let’s get this party started.

Common Nouns That Start with O

First of all, we are going to share with you a list of commonly used nouns that start with O. How many of these nouns starting with O do you regularly make use of?

1. Option

  • Definition: one thing that can be chosen from a set of possibilities
  • Synonyms: choice, alternative
  • Example: Going to college was not an option for me.

2. Outside

  • Definition: the outer side of something
  • Synonyms: exterior, surface
  • Example: Take your boots off outside if they’re muddy.

3. Order

  • Definition: a request to make or deliver food
  • Synonyms: request, instruction
  • Example: What are we going to order today?

4. Odor

  • Definition: a bad smell
  • Synonyms: smell, stench
  • Example: She detected the odor of gas in the room.

5. Ounce

  • Definition: a very small amount of something
  • Synonyms: bit, iota
  • Example: If you had an ounce of sense you wouldn’t believe him!

6. Obesity

  • Definition: the condition of being overweight
  • Synonyms: fatness, corpulence
  • Example: Obesity can increase the risk of heart disease.

7. Opening

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

8. Objective

  • Definition: something that you plan to achieve
  • Synonyms: aim, purpose
  • Example: All mission objectives were fully met.

9. Occupation

  • Definition: a job or profession
  • Synonyms: work, job
  • Example: Ahmed is a writer by occupation.

10. Opportunity

  • Definition: a situation in which it is possible for you to do something
  • Synonyms: chance, moment
  • Example: Opportunity seldom knocks twice.

Positive Nouns That Start with O

We all try to be positive in our general conversations, don’t we? Now how one can make sure that he sounds positive in his communication? Incorporate these positive nouns that start with O into your speech and let their magic work its charm.

1. Organization

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

2. Oath

  • Definition: a serious promise that you will tell the truth
  • Synonyms: pledge, promise,
  • Example: They swore an oath of loyalty to the country.

3. Obligation

  • Definition: a course of action to which a person is morally or legally bound
  • Synonyms: commitment, responsibility
  • Example: You are under no obligation to buy anything.

4. Organ

  • Definition: a part of the body of an animal that performs a particular job
  • Synonyms: part, structure
  • Example: The human brain is an incredibly complicated organ.

5. Organism

  • Definition: an individual animal or plant
  • Synonyms: being, creature
  • Example: DNA carries the genetic blueprint which tells any organism how to build itself.

6. Obedience

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

7. Ovation

  • Definition: a sustained and enthusiastic show of appreciation by means of applause
  • Synonyms: applause, cheering
  • Example: James received the longest ovation of the evening.

8. Opiate

  • Definition: a drug that contains opium
  • Synonyms: drug, sedative
  • Example: Natalia had to take opiates to control the pain.

9. Obelisk

  • Definition: a stone pillar set up as a monument
  • Synonyms: monument, memorial
  • Example: At the middle of the plaza, stood an obelisk.

10. Opus

  • Definition: any work of art
  • Synonyms: composition, work
  • Example: Woody Allen’s latest opus is a musical comedy, shot on location in Venice.

Nouns That Start with O to Describe a Person

Let us now go through some nouns that start with O to describe a person. These nouns will be really helpful in letting you know how people are grouped into different categories on the basis of their beliefs, actions, professions, etc.

1. Offspring

  • Definition: children of a particular parent
  • Synonyms: kid, children
  • Example: Kim visited us on Saturday with all her offspring.

2. Officer

  • Definition: a member of the police force
  • Synonyms: agent, deputy
  • Example: My brother is an officer in the Navy.

3. Owner

  • Definition: a person who owns something
  • Synonyms: possessor, holder
  • Example: Who is the owner of this restaurant?

4. Operator

  • Definition: someone who is skilled at dealing with people
  • Synonyms: worker, dealer
  • Example: He is a computer operator.

5. Originator

  • Definition: one who creates, or originates something
  • Synonyms: architect, pioneer
  • Example: Provide weekly updates to the originator as per schedule.

6. Organizer

  • Definition: a person who arranges an event
  • Synonyms: coordinator, facilitator
  • Example: I would like to talk to the organizer, please.

7. Optimist

  • Definition: a person who tends to be hopeful about the success of something
  • Synonyms: hoper, fantast
  • Example: Tom is such an optimist that he’s sure he’ll soon find a job.

8. Overseer

  • Definition: one who keeps watch over the work of others
  • Synonyms: supervisor, manager
  • Example: The overseer was explaining the job to young trainees.

9. Ogre

  • Definition: a fierce and frightening person
  • Synonyms: monster
  • Example: My boss is a real ogre.

10. Oaf

  • Definition: a man who is clumsy and unintelligent
  • Synonyms: clown
  • Example: You clumsy oaf that’s the second glass you’ve broken today!

Nouns That Start with O for Kindergarten

What are the first words that kids usually learn first? Nouns, isn’t it? Here are some of the most worth nouns that start with the letter O that you can teach to your children.

1. Orange

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

2. Oil

  • Definition: a viscous liquid derived from petroleum, used as a fuel
  • Synonyms: fuel, petrol
  • Example: Oil does not mix with water.

3. Omelet

  • Definition: a dish of beaten eggs cooked in a frying pan
  • Synonyms: scrambled-egg
  • Example: I’ll have an omelet, please.

4. Onion

  • Definition: a swollen edible bulb used as a vegetable
  • Synonyms: shallots
  • Example: There is too much onion in the soup.

5. Oven

  • Definition: an enclosed compartment used for cooking and heating food
  • Synonyms: stove, microwave
  • Example: Mona completely forgot the cake in the oven.

6. Ostrich

  • Definition: a flightless swift-running African bird with a long neck and long legs
  • Synonyms: (none)
  • Example: The ostrich is a flightless bird.

7. Owl

  • Definition: a bird of prey with a loud hooting call
  • Synonyms: owlet, bird-of-prey
  • Example: The owl fluffed out its feathers.

8. Ox

  • Definition: a castrated bull used as a draught animal
  • Synonyms: bull, steer
  • Example: He is as strong as an ox.

9. Outfit

  • Definition: a set of clothes worn for a particular occasion
  • Synonyms: costume, suit
  • Example: I’m not going to wear this outfit for Halloween.

10. Oak

  • Definition: a large tree which bears acorns and typically has lobed deciduous leaves
  • Synonyms: quercus, elm
  • Example: An old oak once stood here.

Useful List of Nouns That Start with O

There are things in this world that are a big help to us human beings. Here are some noun words that start with O that name such things. From this of list of nouns that start with O how many nouns did you know before?

1. Office

  • Definition: a set of rooms used as a place for commercial or professional work
  • Synonyms: workplace, workroom
  • Example: John doesn’t leave the office until eight o’clock.

2. Object

  • Definition: a thing that can be seen, held, or touched
  • Synonyms: thing, item
  • Example: Look, there’s a strange object in the sky!

3. Observation

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

4. Oxygen

  • Definition: the life-supporting component of the air
  • Synonyms: air, oxygenation
  • Example: Oxygen is in high demand these days.

5. Operation

  • Definition: surgery performed on a patient
  • Synonyms: surgery, incision
  • Example: The most recent operation restored his sight.

6. Ornament

  • Definition: an accessory used to make something look more striking
  • Synonyms: trinket, accessory
  • Example: The flowers were put on the table for ornament.

7. Opinion

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

8. Offer

  • Definition: an expression of readiness to do
  • Synonyms: suggestion, proposition
  • Example: What is your offer about this thing?

9. Orphanage

  • Definition: a public institution for the protection of orphans
  • Synonyms: asylum, shelter
  • Example: Mike donated 10 grands to an orphanage.

10. Omnibus

  • Definition: an automotive public vehicle used to carry a large number of passengers
  • Synonyms: bus, vehicle
  • Example: Most of the children ride an omnibus to school each day.

Proper Nouns That Start with O

Here are some proper nouns that start with O that you must get hold of. These nouns include name of people, countries and cities.

1. Oman

  • Definition: Oman is a country on the southeastern coast of the Arabian Peninsula
  • Synonyms: (none)
  • Example: Oman is a member of Gulf Cooperation Committee.

2. Oliver

  • Definition: name of a person
  • Synonyms: (none)
  • Example: Oliver will take you to hospital today.

3. Osaka

  • Definition: Osaka is a commercial center on the Japanese island of Honshu
  • Synonyms: (none)
  • Example: Our flight arrived in Osaka two hours ahead of schedule.

4. Oscar

  • Definition: name of a person
  • Synonyms: (none)
  • Example: Oscar has joined a new club.

5. Oakland

  • Definition: Oakland is a city on the east side of San Francisco Bay, in California
  • Synonyms: (none)
  • Example: There is going to be a concert in Oakland next week.

6. Olivia

  • Definition: name of a person
  • Synonyms: (none)
  • Example: Olivia is in a bad mood today.

7. Oklahoma

  • Definition: Oklahoma is a state in the South Central region of the United States
  • Synonyms: (none)
  • Example: Republican Senator James Milner of Oklahoma, is a real estate developer.

8. Octavia

  • Definition: name of a person
  • Synonyms: (none)
  • Example: Octavia didn’t come to university yesterday!

9. Ottawa

  • Definition: Ottawa is Canada’s capital, in the east of southern Ontario
  • Synonyms: (none)
  • Example: A fast train does the journey to Ottawa in three hours.

10. Ophelia

  • Definition: name of a person
  • Synonyms: (none)
  • Example: Ophelia is the heroine of Shakespeare’s hamlet.

Unusual Nouns That Start with O to Boost Vocabulary

If you open any list of nouns beginning with O anywhere, you will surely come across some nouns that you wouldn’t have seen before. Here are some of those unusual nouns that start with O for you.

1. Orgy

  • Definition: a period when there is too much of a harmful activity
  • Synonyms: debauch, carouse, bacchanalia
  • Example: The rebels went on an orgy of killing.

2. Ordnance

  • Definition: military supplies, especially weapons and bombs
  • Synonyms: guns, artillery
  • Example: There was so much ordnance stored in the warehouse he had to get Ferric to take some home.

3. Omnipotence

  • Definition: unlimited power and the ability to do anything
  • Synonyms: supremacy, pre-eminence
  • Example: That would put a dent in his omnipotence.

4. Oligarchy

  • Definition: government by a small group of powerful people
  • Synonyms: autocracy, totalitarianism
  • Example: Eventually oligarchy took over from democracy.

5. Onyx

  • Definition: a valuable stone that is used in jewelry
  • Synonyms: stone, slab
  • Example: The onyx was shipped to Tijuana to be fabricated into tourist kitsch.

6. Opprobrium

  • Definition: harsh criticism
  • Synonyms: criticism, censure
  • Example: The bombing has attracted international opprobrium.

7. Opulence

  • Definition: the quality of being expensive and luxurious
  • Synonyms: richness, splendor
  • Example: The room was decorated with stagy opulence.

8. Oubliette

  • Definition: a secret dungeon with access only through a trapdoor
  • Synonyms: dungeon, cell
  • Example: Karen trapped Lisa in an oubliette and began to starve her.

9. Ornithology

  • Definition: the study of birds
  • Synonyms: zoology, research
  • Example: Do you understand the system of classification used in ornithology?

10. Osteopathy

  • Definition: the treatment of injuries to bones and muscles using pressure and movement
  • Synonyms: ministration
  • Example: Osteopathy uses massage and gentle manipulation to soften and realign the body.

More Nouns That Start with O

Ready for an extra dose of nouns with letter O? Here are some more interesting O nouns that you should know. These might quench your thirst for knowledge.

1. Origin

  • Definition: the point where something begins
  • Synonyms: beginning, start
  • Example: There is widespread discrimination against doctors of Asian origin.

2. Objection

  • Definition: an expression of disapproval or opposition
  • Synonyms: complaint, grievance
  • Example: The Company has raised no objections to the latest plans.

3. Occasion

  • Definition: a particular time, especially when something happens
  • Synonyms: moment, circumstance
  • Example: They have met on several occasions to discuss this issue.

4. Omen

  • Definition: something that is considered to be a sign of how a future event will take place
  • Synonyms: sign, foreshadowing
  • Example: It’s a good omen for the future.

5. Obstacle

  • Definition: a thing that blocks one’s way or hinders progress
  • Synonyms: barrier, hurdle
  • Example: Her father’s opposition was their only obstacle.

6. Oration

  • Definition: a formal speech about a serious subject
  • Synonyms: speech, address
  • Example: The funeral oration given by her husband moved everyone deeply.

7. Oppression

  • Definition: the state of being subject to oppressive treatment
  • Synonyms: persecution, maltreatment
  • Example: Oppression provoked the people to rebellion.

8. Onslaught

  • Definition: a fierce or destructive attack
  • Synonyms: charge, assault
  • Example: They survived an onslaught by tribesmen.

9. Obeisance

  • Definition: a gesture expressing deferential respect
  • Synonyms: curtesy, bob
  • Example: Was she about to make some obeisance to it?

10. Obloquy

  • Definition: very strong public criticism
  • Synonyms: condemnation, denunciation
  • Example: For many years she had much obloquy to endure.

Nouns That Start with O – Full List (264 Words)

Now that we are done with each and every given noun in detail it’s time we write them all down in a list together with some other ones recommended for you. Here is that list of nouns that start with O.

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

Final Thoughts on Nouns That Start with O

These were all the nouns starting with O that we could fit in in this article. No matter how old you grow, you never stop learning, therefore memorize these nouns beginning with O regardless of your age!

The nouns that start with O that we have discussed are only valuable if you know how to use them correctly in addition to knowing their meaning. As a result, while reading these nouns that start with O, make sure to read them in full detail, including their meanings and synonyms, in order to expand your English vocabulary.

If you do that, you’ll be able to employ them correctly in ordinary conversations, allowing you to improve your language skills even more.

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