245 Nouns That Start with O | Best List with Definitions and Examples

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We understand how exhausting it is to go through all of the nouns that start with O to figure out which ones will work for you. This is why we’ve organized these nouns with respect to the frequency with which they are used. This way you will learn some of the most commonly used as well as seldom used nouns starting with O.

The list of nouns beginning with O is diverse, seemingly unending, and widely used in developing a strong English vocabulary. The nouns given in this article can help you enhance your English language skills through everyday discussion and practice in your daily routine.

Apart from this, you will be able to learn nouns that start with O to define a person such as officer, operator, optimist, outcast, overseer, outlaw, etc. We will also share with you nouns that start with O that carry a positive connotation such as opportunity, obedience, oomph, ovation, odyssey, etc. Inserting these nouns into your daily life talks and writings will make them much more interesting.

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Nouns That Start with O You Always Use

Nouns are an integral component of our daily lives. We can’t imagine talking, writing, or reading without these terms. The following are some nouns that start with O that we always make use of.

1. Opinion

  • Definition: the thoughts or beliefs that a group of people have
  • Synonyms: viewpoint, angle
  • Example: There is a diverse range of opinion on the issue.

2. Outfit

  • Definition: a clothing ensemble often for a special occasion or activity
  • Synonyms: costume, uniform
  • Example: She was wearing an expensive new outfit.

3. Owl

  • Definition: a bird with a flat face and large eyes that hunts small mammals at night
  • Synonyms: night bird, hooter
  • Example: The owl is a predatory bird which kills its prey with its claws.

4. Offer

  • Definition: the act of asking if someone would like to have something or if they would like you to do something
  • Synonyms: suggestion, proposition
  • Example: I must say the offer of two weeks in Hawaii is very tempting.

5. Objection

  • Definition: the act of expressing or feeling opposition to or dislike of something or someone
  • Synonyms: grievance, protestation
  • Example: A couple of people raised objections to the proposal.

6. Occasion

  • Definition: a special or formal event
  • Synonyms: event, circumstance
  • Example: Viola’s party was quite an occasion.

7. Opening

  • Definition: a hole or space that something or someone can pass through
  • Synonyms: hole, aperture
  • Example: The children crawled through an opening in the fence.

8. Option

  • Definition: one thing that can be chosen from a set of possibilities
  • Synonyms: choice, preference
  • Example: Choose the cheapest options for supplying energy.

9. Oil

  • Definition: a thick liquid that comes from petroleum, used as a fuel and for making parts of machines move easily
  • Synonyms: fuel, petrol
  • Example: Oil is refined to remove naturally occurring impurities.

10. Outside

  • Definition: the area or side that faces out or can be seen
  • Synonyms: exterior, surface
  • Example: She stood in the snow on the outside, watching him.

Nouns That Start with O You Usually Use

Everything we can see or talk about is represented by a word. That word is called a noun. Following is a list of nouns starting with O that we usually use in our lives.

1. Object

  • Definition: a material thing that can be seen and touched
  • Synonyms: item, body
  • Example: John was dragging a large object across the hallway.

2. Observation

  • Definition: the fact that you notice or see something
  • Synonyms: examination, consideration
  • Example: Eva has remarkable powers of observation.

3. Origin

  • Definition: the beginning or cause of something
  • Synonyms: start, origination
  • Example: It’s a book about the origin of the universe.

4. Outset

  • Definition: the start or beginning of something
  • Synonyms: starting point, beginning
  • Example: The project was flawed from the outset.

5. Operation

  • Definition: the action of functioning or the fact of being active or in effect
  • Synonyms: functioning, working
  • Example: Government has placed a lot of restrictions on the operation of market forces.

6. Outcome

  • Definition: the way a thing turns out; a consequence
  • Synonyms: end result, consequence
  • Example: It is the outcome of the vote that counts.

7. Outline

  • Definition: the main shape or edge of something, without any details
  • Synonyms: profile, contour
  • Example: She drew the outline of the boat and then colored it in.

8. Organization

  • Definition: the planning of an activity or event
  • Synonyms: planning, arrangement
  • Example: He didn’t want to be involved in the organization of the conference.

9. Oath

  • Definition: a promise, especially that you will tell the truth in a law court
  • Synonyms: pledge, vow, promise,
  • Example: The witness placed her hand on the Bible and took the oath.

10. Office

  • Definition: a room, set of rooms, or building used as a place for commercial, professional, or bureaucratic work
  • Synonyms: workplace, workroom
  • Example: They have offices in Paris, London, and Madrid.

Nouns That Start with O You Often Use

Sentences become clearer when nouns are used because listeners understand what the object being discussed is and what is occurring to that object. Following is a list of nouns that begin with the letter O that we often use in our daily life routine. Try and memorize as many of these nouns beginning with O as possible.

1. Obsession

  • Definition: something or someone that you think about all the time
  • Synonyms: fixation, compulsion
  • Example: I have an obsession with cleanliness.

2. Output

  • Definition: the amount of something produced by a person, machine, or industry
  • Synonyms: production, product
  • Example: Output from the mine ceased in May.

3. Oppression

  • Definition: a situation in which people are governed in an unfair and cruel way and prevented from having opportunities and freedom
  • Synonyms: persecution, maltreatment
  • Example: Several people had experienced the same feeling of oppression.

4. Ox

  • Definition: a castrated bull used as a draught animal
  • Synonyms: bullock, steer
  • Example: Ox is a dangerous animal.

5. Outlook

  • Definition: a person’s point of view or general attitude to life
  • Synonyms: views, interpretation
  • Example: Alex had a practical outlook on life.

6. Overflow

  • Definition: the flowing over of a liquid
  • Synonyms: spillage, flood
  • Example: There was some overflow after heavy rainfall.

7. Obstruction

  • Definition: a thing that impedes or prevents passage or progress; an obstacle or blockage
  • Synonyms: barrier, obstacle
  • Example: Our tractor hit an obstruction.

8. Oscillation

  • Definition: repeated movement from one position to another
  • Synonyms: fluctuation, vibration
  • Example: The oscillations of the needle were so slight they were hard to detect.

9. Objective

  • Definition: something that you aim to do
  • Synonyms: aim, purpose
  • Example: One of my objectives for this year is to increase sales.

10. Occupation

  • Definition: a person’s job
  • Synonyms: profession, job
  • Example: Please state your name, address and occupation.

Nouns That Start with O You Sometimes Use

Let’s now get acquainted with a list of nouns that start with the letter O that people only use sometimes in their daily conversations. From the list of nouns given below, how many did you already know?

1. Obstacle

  • Definition: something that blocks you so that movement, going forward, or action is prevented
  • Synonyms: barrier, hurdle
  • Example: The biggest obstacle in our way was a tree trunk in the road.

2. Overcoat

  • Definition: a long thick coat worn in cold weather
  • Synonyms: greatcoat, long coat
  • Example: Olivia is wearing an overcoat.

3. Outrage

  • Definition: an extremely strong reaction of anger, shock, or indignation
  • Synonyms: fury, anger
  • Example: Her voice trembled with outrage.

4. Onslaught

  • Definition: a very powerful attack
  • Synonyms: assault, attack
  • Example: The city resisted the enemy onslaught for two weeks.

5. Overload

  • Definition: an excessive amount of something
  • Synonyms: excess, overabundance
  • Example: She is dealing with an overload of stress.

6. Oversimplification

  • Definition: the action of describing or explaining something in such a simple way that it is no longer correct or true
  • Synonyms: distortion
  • Example: The book was full of oversimplifications.

7. Overpopulation

  • Definition: the fact of a country or city, etc. having too many people for the amount of food, materials, and space available there
  • Synonyms: excess, profusion
  • Example: Overpopulation is one of the country’s most pressing social problems.

8. Overestimate

  • Definition: a guess that is too high in amount
  • Synonyms: miscalculation, misjudgment
  • Example: The shortfall was caused by an overestimate of revenue last year.

9. Outlet

  • Definition: a way, especially a pipe or hole, for liquid or gas to go out
  • Synonyms: way out, exit
  • Example: The outlet of a water pipe was blocked.

10. Ownership

  • Definition: the act, state, or right of possessing something
  • Synonyms: freehold, proprietorship
  • Example: Do you have any proof of ownership for this car?

Nouns That Start with O You Occasionally Use

Most of the nouns with letter 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. Overcrowding

  • Definition: a situation when a place contains too many people or things
  • Synonyms: deluge, overabundance
  • Example: They are building new classrooms to ease overcrowding.

2. Oversight

  • Definition: a mistake made because of a failure to notice something
  • Synonyms: mistake, error
  • Example: They claimed it was simply an oversight.

3. Outcry

  • Definition: a strong expression of public disapproval or anger
  • Synonyms: outburst, protest
  • Example: A public outcry secured her release from detention.

4. Outgrowth

  • Definition: something that grows out of something else
  • Synonyms: offshoot, bulge
  • Example: Inflation is an outgrowth of war.

5. Outflow

  • Definition: a movement away from a place
  • Synonyms: discharge, outflowing
  • Example: I’m trying to measure the outflow of sewage from that pipe.

6. Overtime

  • Definition: time worked in addition to one’s normal working hours
  • Synonyms: additional time, extra time
  • Example: Approval must be granted for overtime before the work has been performed.

7. Outbreak

  • Definition: a time when something suddenly begins, especially a disease or something else dangerous or unpleasant
  • Synonyms: eruption, outburst
  • Example: They reported a sudden outbreak of the disease in the south of the country.

8. Omen

  • Definition: an event that is thought to tell something about the future
  • Synonyms: sign, foreshadowing
  • Example: Scoring that goal was an omen of things to come.

9. Outburst

  • Definition: a sudden release of strong emotion
  • Synonyms: eruption, explosion
  • Example: Jean’s comments provoked an outburst of anger from the boss.

10. Outpouring

  • Definition: an expression of strong feeling that is difficult to control
  • Synonyms: outflowing, outrush
  • Example: Philip’s death at the age of 35 has occasioned an outpouring of grief.

Nouns That Start with O You Seldom Use

Following are some of the noun words that start with O that are seldom used in talks and writings. Memorizing these noun words starting with O will help you build an impressing self-image for yourself.

1. Overlay

  • Definition: something laid as a covering over something else
  • Synonyms: covering, layer
  • Example: An overlay of wood covers the brick wall.

2. Outpost

  • Definition: a security detachment dispatched by a main body of troops to protect it from enemy surprise
  • Synonyms: post, settlement
  • Example: Some soldiers waited at an outpost deep in the forest.

3. Overhead

  • Definition: the regular and necessary costs, such as rent and heating, that are involved in operating a business
  • Synonyms: costs, expenses
  • Example: We need to reduce our overheads.

4. Overhaul

  • Definition: the act of repairing an engine, machine, etc. so that every part works as it should
  • Synonyms: service, maintenance
  • Example: I took my motorbike in for an overhaul.

5. Overhang

  • Definition: the part of a rock or roof that sticks out over something below
  • Synonyms: projection, protuberance
  • Example: The church is unsafe because it was built on an overhang.

6. Overexploitation

  • Definition: the action or fact of making excessive use of a resource
  • Synonyms: overuse, overutilization
  • Example: The crisis was caused by the overexploitation of fish stocks.

7. Opprobrium

  • Definition: severe criticism and blame
  • Synonyms: criticism, censure
  • Example: Any country trading in these weapons would face international opprobrium.

8. Outhouse

  • Definition: a building such as a shed or barn that is built in the grounds of a house
  • Synonyms: outbuilding, hut
  • Example: My old outhouse is dangerously close to topping out.

9. Opulence

  • Definition: wealth and affluence
  • Synonyms: richness, splendor
  • Example: She stared around her in awe at the sheer opulence of the room.

10. Oubliette

  • Definition: a dungeon with an opening only at the top
  • Synonyms: dungeon, cell
  • Example: Sophia ends up in an oubliette where she reunites with Jack.

Positive Nouns That Start with O

The list of positive nouns that start with O given below contains some very interesting nouns. Go through this list to find out for yourself whether they charm you or not.

1. Oration

  • Definition: a formal speech, especially one given on a ceremonial occasion
  • Synonyms: address, lecture
  • Example: Emma delivered an oration on the value of art in our society.

2. Outreach

  • Definition: an effort to bring services or information to people where they live or spend time
  • Synonyms: advocacy, capacity-building
  • Example: The team was awarded a grant for outreach to the homeless.

3. Obedience

  • Definition: the fact that people or animals do what they are told to do
  • Synonyms: acquiescence, compliance
  • Example: He demands unquestioning obedience from his soldiers.

4. Opportunity

  • Definition: an occasion or situation that makes it possible to do something that you want to do
  • Synonyms: chance, occasion
  • Example: Opportunity, sooner or later, comes to all who work and wish.

5. Ovation

  • Definition: an occasion when a crowd of people expresses great enjoyment and approval of something with loud and long clapping
  • Synonyms: applause, cheering
  • Example: She was given a standing ovation.

6. Outing

  • Definition: a trip taken for pleasure, especially one lasting a day or less
  • Synonyms: trip, jaunt
  • Example: We went for outing towards the north.

7. Orphanage

  • Definition: a residential institution for the care and education of orphans
  • Synonyms: shelter, foundation
  • Example: After the death of his parents, he was raised in an orphanage.

8. Objectivity

  • Definition: the quality of being objective
  • Synonyms: fairness, impartiality
  • Example: The judge had a reputation for complete objectivity.

9. Odyssey

  • Definition: a long, exciting journey
  • Synonyms: adventure, expedition
  • Example: The film follows one man’s odyssey to find the mother from whom he was separated at birth.

10. Oomph

  • Definition: power, strength, or energetic activity
  • Synonyms: stamina, vigor
  • Example: It’s important to have someone with a bit of oomph in charge of the department.

Nouns That Start with O to Describe a Person

In this category, you will be acquainted with nouns that start with O to describe a person and his profession. All of these O nouns describe people for who they are and what they do.

1. Organizer

  • Definition: the person or group who plans and arranges an event or activity
  • Synonyms: coordinator, facilitator
  • Example: We need someone who is a good organizer.

2. Outsider

  • Definition: a person who is not involved with a particular group of people or organization
  • Synonyms: stranger, visitor
  • Example: Outsiders have a glamorized idea of what it is like to work in Hollywood.

3. Owner

  • Definition: someone who owns something
  • Synonyms: possessor, holder
  • Example: Are you the owner of this car?

4. Operator

  • Definition: someone whose job is to use and control a machine or vehicle
  • Synonyms: worker, dealer
  • Example: He is a telephone operator.

5. Originator

  • Definition: the person who first thinks of something and causes it to happen
  • Synonyms: architect, pioneer
  • Example: Wegener was the originator of the theory of continental drift.

6. Officer

  • Definition: a person in the armed forces who has a position of authority
  • Synonyms: agent, chief
  • Example: The officer commanded his men to shoot.

7. Overseer

  • Definition: a person whose job it is to make certain that employees are working or that an activity is being done correctly
  • Synonyms: supervisor, manager
  • Example: The overseers measured the degree of poverty in almost the same way.

8. Outlaw

  • Definition: a person who has broken the law, especially one who remains at large or is a fugitive
  • Synonyms: outcast, pariah
  • Example: Bands of outlaws held up trains.

9. Optimist

  • Definition someone who always believes that good things will happen
  • Synonyms: dreamer, fantast
  • Example: To an optimist every change is a change for the better.

10. Outcast

  • Definition: a person who has been rejected or ostracized by their society or social group
  • Synonyms: reject, leper
  • Example: She went from trusted pal to ostracized outcast overnight.

Nouns That Start with O – Full List (245 Words)

To help you review nouns easily, we prepared a separate list of nouns that start with O contains all the nouns we have learnt above and more useful ones to learn yourself.

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

Final Thoughts on Nouns That Start with O

Thank you for going through this article on nouns that start with O. It makes no difference whether you are a student or an expert; this list was constructed in such a way that any person of any skill level can just read through it and learn some new nouns starting with O.

The English language is abundant of nouns that start O, but we have only included a few of them in our list to provide our readers with a nice and tranquil reading experience. We trust that some of the nouns beginning with O in this list will find their way into your vocabulary and help you improve your daily as well as formal communication.