280+ Nouns That Start with O | Definitions, and Examples Included

We are back again with another great collection of carefully curated nouns that start with O. Noun is usually the first among parts of speech.

It is also the most significant one as it encompasses the names of the objects, people, and concepts that make up our life. Nouns seem like real MVPs!

Without nouns, we would be clueless about the identification of objects. To save from such trouble, we have brought together a diverse range of nouns that start with O.

After devouring these you will definitely struggle less with your English vocabulary. Sounds like a bonus right?

Nouns beginning with O have been divided into eight categories containing ten nouns starting with O. We have different levels along with a separate compilation of proper nouns, descriptive nouns and positive nouns.

So let’s indulge in this interesting collection to expand our knowledge and make our language refined and clear.

Most Common Nouns That Start with O

It is always wise to start with the most common vocabulary and slowly build one’s way towards the complicated one. Following the same tradition, we present the most commonly used nouns that start with O.

1. Order

• Definition: an authoritative command or instruction
• Synonyms: command, instruction
• Example: The soldiers fired as soon as their commander gave the order.

2. Odor

• Definition: an unpleasant smell
• Synonyms: smell, stench
• Example: This deodorant claims to remove bad odor in first use.

3. Oil

• Definition: a thick sticky liquid
• Synonyms: fuel, petrol
• Example: Put a tablespoon of oil into the batter.

4. Orange

• Definition: a citrus fruit
• Synonyms: (none)
• Example: We gifted her a basket of homegrown oranges.

5. Ounce

• Definition: a small quantity
• Synonyms: bit, iota
• Example: She didn’t have an ounce of respect for her father.

6. Owner

• Definition: someone who possesses something
• Synonyms: possessor, holder
• Example: I want to meet the owner of this mansion.

7. Office

• Definition: a place used for working
• Synonyms: workplace, workroom
• Example: She had a beautiful glass office.

8. Outside

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

9. Opening

• Definition: something that is uncovered or unblocked
• Synonyms: hole, aperture
• Example: She peeked through the tiny opening in the wall.

10. Officer

• Definition: an authoritative figure
• Synonyms: agent, chief
• Example: The officer commanded him to surrender immediately.

Nouns That Start with O – Beginner Level

Beginners are very courageous in taking the first step. Once the first step is taken, the rest of the journey becomes easy. For our beginners, we have ten nouns that start with the letter O.

1. Option

• Definition: one possibility out of a set of possibilities
• Synonyms: choice, inclination
• Example: We do not have any other option than to pay the bills.

2. Observation

• Definition: a keen examination
• Synonyms: opinion, consideration
• Example: According to my observation they never left the building.

3. Origin

• Definition: the roots or beginning
• Synonyms: start, initiation
• Example: My name has Arabic origin.

4. Opinion

• Definition: a thought or an idea
• Synonyms: viewpoint, perspective
• Example: Your opinion will be welcomed by the board.

5. Operation

• Definition: the state of working
• Synonyms: functioning, operational
• Example: Company’s operation will be affected by the instability in the market.

6. Organization

• Definition: a systematic plan or a well-structured institute
• Synonyms: planning, preparation
• Example: This organization is committed to the welfare of the poor.

7. Offer

• Definition: a proposed suggestion
• Synonyms: recommendation, proposal
• Example: Your offer is very tempting to be honest.

8. Objection

• Definition: discontentment or rejection
• Synonyms: complaint, protestation
• Example: The director had a lot of objections to our proposal.

9. Outlet

• Definition: a portal used for exit
• Synonyms: exit, gateway
• Example: We tried to unblock the outlet of the pipe.

10. Occasion

• Definition: an event
• Synonyms: happening, circumstance
• Example: On the occasion of my sister’s wedding, I would like to make a toast.

Nouns That Start with O – Medium Level

After the beginner level, we congratulate you on entering the medium level! Bravo! You’re making good progress there champ! Let’s now find out more fun noun words that start with O.

1. Outset

• Definition: the beginning
• Synonyms: basis, beginning
• Example: We had sensed a risk from the outset of the project.

2. Outcome

• Definition: a final result
• Synonyms: aftermath, consequence
• Example: For a positive outcome, you need to put in more effort in this task.

3. Occupation

• Definition: a position or a job
• Synonyms: profession, job
• Example: Please tell us your occupation.

4. Organizer

• Definition: someone who arranges an event
• Synonyms: coordinator, implementer
• Example: Our event was managed by an excellent organizer.

5. Outsider

• Definition: someone who is not a part of an organization
• Synonyms: alien, stranger
• Example: Outsiders are not allowed at this party.

6. Obstacle

• Definition: a hindrance or a blockage
• Synonyms: barrier, difficulty
• Example: We faced many obstacles while hiking.

7. Obsession

• Definition: something that becomes the center of one’s imagination
• Synonyms: fixation, fascination
• Example: Pam has an obsession with costumes.

8. Output

• Definition: the outcome or end product
• Synonyms: production, creation
• Example: Your factory’s output has increased since the previous month.

9. Outline

• Definition: the border of an object
• Synonyms: silhouette, contour
• Example: The marble floor had a black outline to it.

10. Outlook

• Definition: a perspective
• Synonyms: views, interpretation
• Example: I always try to have a positive outlook toward life.

Nouns That Start with O – Hard Level

Now that you have moved past the medium level, a more sophisticated collection of nouns beginning with O awaits you. There is no need to fret at the idea of entering a more challenging level because we know you’ll ace it!

1. Outbreak

• Definition: a sudden beginning or eruption
• Synonyms: upsurge, outburst
• Example: We have taken all the necessary measures to tackle the disease outbreak.

2. Outburst

• Definition: a sudden spontaneous expression of emotions
• Synonyms: eruption, burst
• Example: Her mean comments resulted in an outburst of tears for me.

3. Oppression

• Definition: a state of suppressing the rights of the less privileged
• Synonyms: persecution, cruelty
• Example: We need to raise our voice against the oppression of poor.

4. Oath

• Definition: a promise taken in court
• Synonyms: pledge, vow
• Example: She took an oath at the court.

5. Omen

• Definition: a sign that predicts future
• Synonyms: sign, vision
• Example: Her sudden detachment is not a good omen.

6. Obstruction

• Definition: a hindrance in the way of success
• Synonyms: barrier, impediment
• Example: They were trying their best to get rid of the obstruction.

7. Oversimplification

• Definition: something that is made easy in an incorrect way
• Synonyms: distortion, falsification
• Example: I am not believing his oversimplification of the matter.

8. Overpopulation

• Definition: a disproportionate increase in the number of people
• Synonyms: excess, abundance
• Example: Overpopulation is the main cause of pollution.

9. Outcry

• Definition: a clear expression of discontent
• Synonyms: outburst, objection
• Example: She will not hold back from a public outcry to gain the sympathies of people.

10. Oscillation

• Definition: side-to-side movement
• Synonyms: fluctuation, pulsation
• Example: Slight oscillation was observed but it was hard to detect.

Nouns That Start with O – Expert Level

Since you nailed the hard level, you have a very good chance of becoming an expert with O nouns. So check out this collection along with synonyms and examples to enhance your knowledge about nouns with letter O.

1. Outrage

• Definition: extreme anger
• Synonyms: fury, rage
• Example: He faced public outrage for allegations of abuse.

2. Overseer

• Definition: a supervisor for employees
• Synonyms: administrator, manager
• Example: The overseer could sense that the workers will soon demand a break.

3. Outlaw

• Definition: someone who breaks the law
• Synonyms: outcast, exile
• Example: They are on a lookout for a band of outlaws.

4. Overload

• Definition: an abundance of something
• Synonyms: excess, surplus
• Example: She is tired of the work overload.

5. Optimist

• Definition: a believer of positivity
• Synonyms: dreamer, idealist
• Example: Sam is an optimist so he will handle the news.

6. Oration

• Definition: a formal speech
• Synonyms: address, sermon
• Example: Peter’s oration at the closing ceremony was mind blowing.

7. Outpost

• Definition: a security placement of troops to prevent an unexpected enemy attack
• Synonyms: post, garrison
• Example: We could see some soldiers at the outpost.

8. Overhaul

• Definition: proper repair of a machine
• Synonyms: service, upkeep
• Example: My car is performing better after the overhaul.

9. Outhouse

• Definition: a shed build on the grounds of a property
• Synonyms: cabin, hut
• Example: I want to renovate the outhouse.

10. Outcast

• Definition: someone who is rejected by the society
• Synonyms: castoff, leper
• Example: Iris has been an outcast since their high school days.

Positive Nouns That Start with O

Words exude positivity. The kind of vocabulary one uses makes an impact on the listener. So positive words can always brighten up the room! Let’s get a glance at positive nouns that start with O.

1. Ownership

• Definition: rightful possession of something
• Synonyms: right, proprietorship
• Example: I want to see your papers for the ownership of this property.

2. Objective

• Definition: an aim
• Synonyms: target, purpose
• Example: Your teaching strategy perfectly match the objectives of the institute.

3. Obedience

• Definition: prompt following of instructions
• Synonyms: compliance, compliance
• Example: I admire the obedience of your students.

4. Oomph

• Definition: an energetic edge
• Synonyms: stamina, strength
• Example: A splash of yellow can provide oomph to your apartment.

5. Opportunity

• Definition: a sought-after occasion that helps one achieve his/her objectives
• Synonyms: chance, circumstance
• Example: If you stay optimistic, opportunities will come your way.

6. Ovation

• Definition: an energetic cheering of the crowd
• Synonyms: applause, clapping
• Example: The judges gave our team a standing ovation.

7. Outing

• Definition: a trip
• Synonyms: tour, jaunt
• Example: I love to go on outings every weekend.

8. Orphanage

• Definition: a shelter for orphans
• Synonyms: hostel, foundation
• Example: We used to live in the same orphanage.

9. Objectivity

• Definition: the state of being logical and objective
• Synonyms: fairness, neutrality
• Example: My comments were given with utter objectivity.

10. Opulence

• Definition: extreme wealth
• Synonyms: richness, lushness
• Example: The castle interior reflected absolute opulence.

Proper Nouns That Start with O

Proper nouns are very diverse. With each passing day, new proper nouns get introduced to the world. Let’s see how any new proper nouns that start with O we learn under this category.

1. Oman

• Definition: a country in southwestern Asia
• Synonyms: (none)
• Example: We visited beautiful mosques in Oman.

2. Olivia

• Definition: a feminine name
• Synonyms: (none)
• Example: I am going to have dinner with Olivia.

3. Oldsmobile

• Definition: a brand of American automobiles
• Synonyms: (none)
• Example: I trust the quality of cars made by Oldsmobile.

4. Oakland

• Definition: a city in California
• Synonyms: (none)
• Example: We can go to Oakland together.

5. Osella

• Definition: an Italian car manufacturer
• Synonyms: (none)
• Example: I think Osella has the best racing cars!

6. Oliver

• Definition: a name for boys
• Synonyms: (none)
• Example: Oliver is my son.

7. Osaka

• Definition: a company that specializes in making batteries
• Synonyms: (none)
• Example: You can buy a good battery from Osaka.

8. Octavia

• Definition: a car brand
• Synonyms: (none)
• Example: He gifted me an Octavia for my birthday.

9. Oscars

• Definition: awards for the film industry
• Synonyms: (none)
• Example: We were watching Oscars on television.

10. Ordos

• Definition: a city in China
• Synonyms: (none)
• Example: She left for Ordos last night.

Nouns That Start with O to Describe Things

Without nouns, we would struggle immensely with describing our feelings or hard to convey abstract concepts. Nouns enable us to have names for unexplainable phenomenon. So let’s learn about things that start with O.

1. Object

• Definition: a tangible material
• Synonyms: item, bulk
• Example: She was hit by a sharp object.

2. Overcoat

• Definition: a long coat
• Synonyms: greatcoat, topcoat
• Example: I loved your white overcoat.

3. Ostrich

• Definition: an African bird
• Synonyms: (none)
• Example: We saw an Ostrich at the zoo.

4. Ox

• Definition: a domesticated bull
• Synonyms: bull, steer
• Example: Most of the weight was carried by the ox.

5. Outfit

• Definition: a set of clothes worn for a particular occasion or activity
• Synonyms: costume, dress
• Example: I am in love with your neon outfit.

6. Owl

• Definition: a bird that stays up at night
• Synonyms: night bird, hooter
• Example: She is as wise as an owl.

7. Organ

• Definition: a body part
• Synonyms: part, structure
• Example: Thank God his vital organs are undamaged.

8. Omelet

• Definition: eggs beaten together as a batter and cooked on a pan
• Synonyms: scrambled-egg
• Example: I always have an omelet in breakfast.

9. Onion

• Definition: a layered vegetable
• Synonyms: shallots
• Example: The onion made my eyes water.

10. Oven

• Definition: a heated compartment used for baking
• Synonyms: stove, microwave
• Example: I bought a new oven for my bakery.

Nouns That Start with O – Full List (280+ Words)

Take a look at the list of nouns that start with O. This is where all the categories are merged for your ease. You can go through them and check your memory.

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

Final Thoughts on Nouns That Start with O

That brings us to the end of this informative roller coaster. We really hope had a good time getting all the new and interesting knowledge.

These nouns that start with O will help you improve your daily conversations. We always have more fun knowing that we wouldn’t get stuck with vocabulary.

Knowing about these interesting nouns that start with O will give you the confidence to speak your mind without an ounce of fear.

All of these nouns starting with O were explicitly categorized for your convenience. We hope that you use them in your day-to-day dealings so that you never forget them.

All of the mentioned nouns beginning with O were fun in our eyes but which ones did you like the most?