Long words that start with O can help you sound more confident and expressive in English. Some of these words may look difficult at first, but once you understand their meanings, they become easy and useful in daily conversation and writing. In this article, you will find common and meaningful long O words that can improve your vocabulary step by step. Take your time, read through the words, and enjoy learning something new.
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List of Long Words That Start with O
This list features long words that start with O to help you expand your vocabulary and use them with confidence. Explore the words and start including them in your writing and conversations today. You can also check other letters to find more interesting words 👇👇👇
A | B | C | D | E | F | G | H | I | J | K | L | M | N | P
| objective | obligation |
| observable | obsession |
| outspoken | optimistic |
| ordinance | overactive |
| overnight | operation |
| offensive | organizer |
| oppression | opposition |
| observation | outspokenly |
| operational | occupation |
| outrageous | overconfident |
| organization | occasionally |
| objectivity | operationally |
| opportunistic | overstatement |
| overreaction | overanalyze |
| overeducated | overqualified |
| overestimate | overexposed |
| overprotect | overthinking |
| oversensitive | overspending |
| oversleeping | overweighted |
| overbalanced | overdecorate |
| orchestral | orchestrate |
| ornamental | originally |
| originality | oscillation |
| orientation | outperformed |
| outnumbered | outstretched |
| outplacement | outdistance |
| outmaneuver | outsmarted |
| outstanding | overabundant |
| overambition | overburdened |
| overcapacity | overcautious |
| overcleaning | overcreative |
| overdramatic | overeating |
| overfamiliar | overgenerous |
| overhearing | overheating |
| overindulge | overinflated |
| overinvolved | overlearning |
| overmedicate | overmoderate |
| overoptimism | overorganized |
| overregulate | overstrength |
| overtighten | overtraining |
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Common Long Words that Start with O
| objective | obligation |
| observation | operational |
| organization | opposition |
| occupation | optimistic |
| outspoken | overnight |
| observable | obsession |
| ordinance | opportunity |
| occasional | objectivity |
| overwhelmingly | overpopulation |
| overconfidence | overestimate |
| overreaction | overthinking |
| overspending | oversleeping |
| overqualified | overexposed |
| outstanding | orchestral |
| orchestrate | ornamental |
| originality | oscillation |
| orientation | outspokenly |
| outrageous | opportunistic |
| overprotective | overstatement |
| overachievement | overestimation |
| overcompensate | organizational |
| organizationally | operationally |
| overgeneralize |
Eleven Letter Long Words Starting with O
| Obfuscating | Obfuscation |
| Objectified | Objectively |
| Objectivism | Objectivist |
| Objectivity | Obligations |
| Obliterated | Obliterates |
| Obscenities | Obscuration |
| Obscurities | Observables |
| Observances | Observation |
| Observatory | Obsessively |
| Obstetrical | Obstinately |
| Obstructing | Obstruction |
| Obstructive | Obviousness |
| Occupancies | Occupations |
| Occurrences | Odontogenic |
| Omnipotence | Omnipresent |
| Omniscience | Oncogenesis |
| Opportunism | Opportunist |
| Opportunity | Oppositions |
| Oppressions | Optionality |
| Optometrist | Orchestrate |
| Orchiectomy | Orderliness |
| Ordinations | Organically |
| Orientalism | Orientalist |
| Orientation | Originality |
| Originating | Origination |
| Originators | Ornamentals |
| Ornithology | Orthodontia |
| Orthodontic | Orthodoxies |
| Orthography | Orthonormal |
| Orthopedics | Orthopedist |
| Orthostatic | Oscillating |
| Oscillation | Oscillators |
| Oscillatory | Ostentation |
| Osteoblasts | Osteoclasts |
| Osteopathic | Outbuilding |
| Outcropping | Outcrossing |
| Outdoorsman | Outdoorsmen |
| Outfielders | Outnumbered |
| Outpatients | Outperforms |
| Outpourings | Outsmarting |
| Outsourcing | Outstanding |
| Outstripped | Outweighing |
| Ovariectomy | Oviposition |
| Oxygenating | Oxygenation |
Ten Letter Long Words Starting with O
| Obediently | Obfuscated | Obituaries |
| Objections | Objectives | Obligation |
| Obligatory | Obliterate | Obsequious |
| Observable | Observance | Obsessions |
| Obstetrics | Obstructed | Obtainable |
| Occasional | Occasioned | Occidental |
| Occlusions | Occupation | Occurrence |
| Oceanfront | Octahedral | Oculomotor |
| Oesophagus | Oestradiol | Offensives |
| Officially | Officiants | Officiated |
| Offloading | Offsetting | Offshoring |
| Oftentimes | Oligomeric | Omnipotent |
| Omniscient | Omnivorous | Oncologist |
| Ontologies | Opalescent | Operations |
| Operatives | Ophthalmic | Opposition |
| Oppressing | Oppression | Oppressive |
| Oppressors | Optimality | Optimising |
| Optimistic | Optimizers | Optimizing |
| Optionally | Optometric | Orangutans |
| Orchestral | Orchestras | Ordinances |
| Ordinaries | Ordinarily | Ordinating |
| Ordination | Ordonnance | Organelles |
| Organisers | Organising | Organismal |
| Organizers | Organizing | Orientated |
| Originally | Originated | Originates |
| Originator | Ornamental | Ornamented |
| Orphanages | Orthogonal | Orthopedic |
| Orthoptera | Oscillates | Oscillator |
| Osmolality | Ostensible | Ostensibly |
| Osteoblast | Osteoclast | Osteopaths |
| Osteopathy | Ostracized | Otherworld |
| Outfielder | Outfitters | Outfitting |
| Outlandish | Outpatient | Outperform |
| Outpouring | Outputting | Outrageous |
| Outriggers | Outsourced | Outsources |
| Outstation | Outweighed | Overactive |
| Overbooked | Overbought | Overburden |
| Overcharge | Overcoming | Overdosage |
| Overdosing | Overdrafts | Overeating |
| Overflowed | Overgrowth | Overhauled |
| Overheated | Overlapped | Overlaying |
| Overloaded | Overlocker | Overlooked |
| Overnights | Overpasses | Overpriced |
| Overridden | Overriding | Overruling |
| Overseeing | Overshadow | Overstated |
| Overstocks | Oversupply | Overtaking |
| Overthrown | Overturned | Overvalued |
| Overweight | Overwhelms | Overwinter |
| Overworked | Overwrites | Ownerships |
| Oxygenated | Oxygenates |
Long Words Starting with O And Ending in D
| Obfuscated | Orientated |
| Obstructed | Originated |
| Occasioned | Ornamented |
| Officiated | Ostracized |
| Otherworld | Outsourced |
| Outweighed | Overbooked |
| Overflowed | Overhauled |
| Overheated | Overlapped |
| Overloaded | Overlooked |
| Overpriced | Overstatedd |
| Overturned | Overvalued |
| Overworked | Oxygenated |
Long Words Starting with O And Ending in G
| Offloading | Offsetting |
| Offshoring | Oppressing |
| Optimising | Optimizing |
| Ordinating | Organising |
| Organizing | Outfitting |
| Outpouring | Outputting |
| Overcoming | Overdosing |
| Overeating | Overlaying |
| Overriding | Overruling |
| Overseing | Overtaking |
Long Words Starting with O And Ending in S
| Obligations | Observances |
| Obliterates | Obviousness |
| Obscenities | Occupancies |
| Obscurities | Occupations |
| Observables | Occurrences |
| Oncogenesis | Oncologists |
| Oppositions | Oppressions |
| Orderliness | Ordinations |
| Originators | Ornamentals |
| Orthodoxies | Orthopedics |
| Oscillators | Osteoblasts |
| Osteoclasts | Outfielders |
| Outpatients | Outperforms |
| Outpourings | Outpourings |
| Overcharges | Overflights |
| Overshadows | Overzealous |
Long Words With Vowels After O
| OA | OE | OI | OO | OU |
|---|---|---|---|---|
| oafishness | oeillades | oinologies | oolongtea | outspokenly |
| oakmosses | oesophageal | ointments | outlandish | |
| oarlocks | oenologies | oilcans | outnumbered | |
| oathbreakers | oeuvre | outstretch | ||
| oathkeeping | outpouring | |||
| oathsayers | outstanding | |||
| outspoken | ||||
| outlasting | ||||
| outwitting | ||||
| outreach |
Rare or Interesting Long Words Starting With O
| Word | Meaning/Usage |
|---|---|
| Obstreperous | Noisy and difficult to control |
| Oligochaetous | Relating to a subclass of worms (earthworms) |
| Osteopathically | In a manner related to osteopathy or bone treatment |
| Oxyphenbutazone | A chemical compound, rarely used outside chemistry |
| Omphalopsychite | A person who believes in thinking from their navel (rarely used, historical term) |
| Ornithorhynchidae | The family of animals including the platypus |
| Overintellectualize | To analyze or think about something in an overly intellectual way |
| Oxymoronically | In a manner that uses contradictory terms |
| Obfuscational | Related to making something obscure or unclear |
| Octodecillion | A very large number (1 followed by 57 zeros in the US system) |
Popular Long Words Starting with O
| Word | Meaning |
|---|---|
| Obfuscation | The act of making something unclear or hard to understand |
| Observation | The act of noticing or examining something carefully |
| Obstinately | Stubbornly refusing to change one’s opinion or action |
| Obtainment | The act of acquiring or gaining something |
| Occupations | Jobs or professions that people do for a living |
| Officiating | Acting in an official capacity, like a referee or judge |
| Offensive | Causing displeasure, anger, or resentment |
| Offshoots | Secondary or derived things that come from something else |
| Omnipotence | The state of having unlimited power |
| Omniscience | The state of knowing everything |
| Onomatopoeia | A word that imitates the sound it represents |
| Operability | The quality of being able to operate or function |
| Opportunity | A favorable situation or chance to do something |
| Opposition | Resistance or disagreement against something |
| Optimistically | In a way that shows hope and confidence for the future |
| Orchestrate | To arrange or coordinate carefully |
| Ordinarily | Usually or normally |
| Organicism | The idea that things are interconnected like a living organism |
| Organizational | Relating to the structure or functioning of an organization |
| Ornamentation | Decorative elements added to something |
| Outlandishly | In a strange, unusual, or bizarre way |
| Outmaneuver | To skillfully outsmart or gain advantage over someone |
| Outplacement | Assistance given to laid-off employees to find new jobs |
| Outperform | To do better than others or exceed expectations |
| Outstanding | Exceptionally good or clearly noticeable |
| Overabundant | Exceedingly abundant or excessive |
| Overestimate | To estimate something to be more than it actually is |
| Overexposed | Exposed too much, often to light or public attention |
| Overwhelming | Very great in amount or effect; intense |
| Oxymoronic | Containing contradictory terms |
| Obstreperous | Noisy, unruly, or difficult to control |
| Opportunist | Someone who takes advantage of circumstances for personal gain |
| Oscillating | Moving back and forth regularly |
| Overzealous | Excessively enthusiastic or eager |
| Outrageously | In an extremely shocking or unusual manner |
FAQs About Long Words Starting With O
Q1. What are long words that start with O?
Long words that start with O are English words beginning with the letter O and typically have 9 or more letters. They can be formal, technical, or commonly used in literature. Examples include observation, omnipotence, obstreperous, onomatopoeia, and orchestrate.
Q2. Can you provide some common long words starting with ‘O’?
Absolutely! Here are some commonly used long O-words:
• Observation
• Obfuscation
• Omnipotence
• Obstreperous
• Onomatopoeia
• Orchestrate
• Opportunity
• Outstanding
• Overestimate
Q3. Can you give some example sentences?
Sure! Here are a few sentences using long O-words:
• The scientist made a detailed observation of the experiment.
• The instructions were full of unnecessary obfuscation.
• Many legends describe gods with omnipotence and unlimited power.
• The crowd became obstreperous during the heated debate.
• Words like buzz and clang are examples of onomatopoeia.
• The event planner worked hard to orchestrate the perfect ceremony.
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