222 Common Nouns that Start with O in English

If you’re like almost everyone else in this world, the definition of a noun was probably pounded into your brain at a young age. Elementary school teachers go above and beyond teaching students that a noun is a person, place, or thing. Of course, your particular definition could vary a bit. For instance, maybe the word object or something similar is thrown in there.

Nouns That Start with O

What Are Nouns That Start With O?

O isn’t necessarily a letter that people think about words starting with. In fact, you might believe there aren’t many nouns, verbs, or adjectives that begin with the fifteenth letter of the alphabet. However, that simply is not true.

There are many words in the English language that start with O. Don’t fret, though. We don’t expect you to merely take these words for it. Instead, stick around and read on to the next section. It is a list containing various nouns which begin with the O sound.

List of Nouns that Start with O

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

Nouns that Start with O

Oak

Obviously, nouns that start with O come in many different shapes and sizes. Oak is a short three-letter word and is the name of a tree. Not only that but the noun can be used to describe the wood from an oak tree as well.

Oasis

Music buffs, we are not talking about the band Oasis, although, that is a noun too. The oasis that’s being referred to here is a fertile area in a dry region. Those who find such places often never want to leave because they’re beautiful, calming, and relaxing.

Ohio

Ohio is only one of fifty states in the United States. It isn’t a small spot, either, so you’ve likely heard the name before. Research reveals that Ohio features an area of 44,825 square miles. It was home to a population of 11.80 million in 2020. However, that number very well could have increased by now, and why wouldn’t it have? People flock to this location for reasons like the weather, the Pro Football Hall of Fame, and the Rock and Roll Hall of Fame.

Office

Next up on this list of nouns that start with O is the word office. An office is a place where people go to perform work duties. This is usually at a location other than their houses, but those who have remote jobs sometimes have home offices as well.

Okra

The okra plant creates long edible beaked pods. This type of food can be eaten alone, as some people enjoy it fried. Meanwhile, others add okra to dishes such as gumbo or vegetable stew.

Some Last Thoughts

So, as you can see, there are plenty of nouns that start with O. The ones listed here barely even begin to scratch the surface. If you want to learn about others, type in a few keywords and perform a Google search. Or are you not about technology? That’s fine. Head to the library or get out that dusty dictionary on the bookshelf and see what you can find.

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