9,371 Words That Start With "O"
9,371 words that start with "O" in our 199K-word dictionary.
Browse the complete list of 9,371 English words starting with "O". Each word in the grid below shows its IPA pronunciation, CEFR difficulty level (A1 beginner up to C2 mastery), and a one-line plain-English definition. Click any word to open its full dictionary entry. Use the filters to narrow by length, part of speech, or learner level.
Most Common Words That Start With "O" (Top 1k)
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Obvious /ˈɒbviəs/adj A2
Easy to see or understand; not hidden or difficult.
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Of /əv/prep A1
A preposition showing what something is made of or who owns it.
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Off /ɔːf/adv A1
Not on; separated from something. Go away from.
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Oil /ɔɪl/noun A1
Liquid fat used for cooking or making machines work.
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Ok /ˌoʊˈkeɪ/adj A1
Good enough; not bad, but not great.
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Okay /oʊˈkeɪ/interj A1
A word that shows you agree or understand something
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Old /oʊld/adj A1
Having been alive or existing for a long time.
Less Common Words That Start With "O" (Top 5k+)
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Oar /ɔːr/noun B1
A stick with a flat end that rowers use to move boats forward.
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Oasis /oʊˈeɪ.sɪs/noun B2
A green, watery spot in the middle of a desert where plants and people can survive.
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Object /ˈɒbdʒɪkt/noun A1
Any item or thing you can hold or see.
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Obscure /əbˈskjʊr/adj C2
Not clear or easy to understand; unclear and ambiguous; also, not well-known or famous; dim and hard to see.
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Observe /əbˈzɜːv/verb B1
To watch and notice something carefully.
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Obtain /əbˈteɪn/verb B1
To get or receive something that you want or need.
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Occupy /ˈɑːkjupaɪ/verb A2
To live in a place or to take up someone's time or thoughts.
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Occur /əˈkɜːr/verb A2
When something happens at a particular time.
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Ocean /ˈoʊʃən/noun A1
The largest saltwater environment on Earth with waves and marine life.
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Octopus /ˈɒk.tə.pʊs/noun B1
A soft sea animal with eight arms and no bones, able to change its color.
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Ode /oʊd/noun C2
A praise poem that celebrates something or someone; a formal, often lengthy poem expressing admiration.
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Offense /əˈfɛns/noun B1
An action that breaks the law or rules; a crime.
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Offer /ˈɔːfər/verb A2
Give or propose something to someone; ask if they want it.
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Office /ˈɔːfɪs/noun A1
A place where people work, usually with desks and computers.
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Officer /ˈɔːfɪsər/noun A2
A person with an official position and responsibility; often in police or military.
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Often /ˈɔːfən/adv A1
Happening or done many times, not rarely.
577 More Words That Start With "O" (definitions coming soon)
Words That Start With "O" by Length
2 Letter Words That Start With "O" (21)
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Of /əv/prep A1
A preposition showing what something is made of or who owns it.
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Ok /ˌoʊˈkeɪ/adj A1
Good enough; not bad, but not great.
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On /ɑn/prep A1
Something touching or resting on top of something else.
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Or /ɔːr/conj A1
Used to show options or choices between things.
See all 21 2-letter words that start with "O" →
3 Letter Words That Start With "O" (91)
See all 91 3-letter words that start with "O" →
4 Letter Words That Start With "O" (217)
See all 217 4-letter words that start with "O" →
5 Letter Words That Start With "O" (301)
See all 301 5-letter words that start with "O" →
6 Letter Words That Start With "O" (549)
See all 549 6-letter words that start with "O" →
7 Letter Words That Start With "O" (921)
See all 921 7-letter words that start with "O" →
8 Letter Words That Start With "O" (1,360)
See all 1,360 8-letter words that start with "O" →
9 Letter Words That Start With "O" (1,467)
See all 1,467 9-letter words that start with "O" →
10 Letter Words That Start With "O" (1,369)
See all 1,369 10-letter words that start with "O" →
11 Letter Words That Start With "O" (1,112)
See all 1,112 11-letter words that start with "O" →
12 Letter Words That Start With "O" (800)
See all 800 12-letter words that start with "O" →
13 Letter Words That Start With "O" (531)
See all 531 13-letter words that start with "O" →
14 Letter Words That Start With "O" (372)
See all 372 14-letter words that start with "O" →
15 Letter Words That Start With "O" (260)
Words That Start With "O" by Part of Speech
Nouns That Start With "O" (52)
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Oil /ɔɪl/noun A1
Liquid fat used for cooking or making machines work.
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One /wʌn/noun A1
The smallest whole number.
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Organization /ˌɔrɡənɪˈzeɪʃən/noun B1
A company, club, or group working together for common goals.
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Origin /ˈɔrɪdʒɪn/noun B1
Where something began or was created; its source.
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Observation /ˌɒbzərˈveɪʃən/noun B1
When you notice and watch something carefully to understand it.
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Ocean /ˈoʊʃən/noun A1
The largest saltwater environment on Earth with waves and marine life.
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Onion /ˈʌnjən/noun A1
A vegetable that makes you cry, used in cooking.
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Order /ˈɔːrdər/noun A1
A request asking someone to make, deliver, or sell you something.
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Oven /ˈʌvən/noun A1
A hot box where you cook food, like baking cookies or roasting chicken.
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Owner /ˈoʊnər/noun A1
The person that something belongs to.
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Oar /ɔːr/noun B1
A stick with a flat end that rowers use to move boats forward.
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Object /ˈɒbdʒɪkt/noun A1
Any item or thing you can hold or see.
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Occasion /əˈkeɪʒən/noun A2
A special event or moment when something takes place.
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Octopus /ˈɒk.tə.pʊs/noun B1
A soft sea animal with eight arms and no bones, able to change its color.
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Offense /əˈfɛns/noun B1
An action that breaks the law or rules; a crime.
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Office /ˈɔːfɪs/noun A1
A place where people work, usually with desks and computers.
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Officer /ˈɔːfɪsər/noun A2
A person with an official position and responsibility; often in police or military.
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Offshoring /ˌɔːfˈʃɔːrɪŋ/noun B2
When a company moves its operations or factories to another country, usually to save money on labor costs.
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Opening /ˈoʊpənɪŋ/noun A2
A space where something is open; or the beginning of an event.
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Opinion /əˈpɪnjən/noun A1
What you think or believe about something; your personal view or judgment.
See all 52 nouns that start with "O" →
Verbs That Start With "O" (26)
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Organize /ˈɔrɡənaɪz/verb A2
To arrange things neatly, or to create a team or plan.
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Owe /oʊ/verb A1
You owe money or thanks when someone gave you something you must give back.
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Own /oʊn/verb A1
To have something that belongs to you.
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Occur /əˈkɜːr/verb A2
When something happens at a particular time.
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Offer /ˈɔːfər/verb A2
Give or propose something to someone; ask if they want it.
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Observe /əbˈzɜːv/verb B1
To watch and notice something carefully.
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Obtain /əbˈteɪn/verb B1
To get or receive something that you want or need.
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Occupy /ˈɑːkjupaɪ/verb A2
To live in a place or to take up someone's time or thoughts.
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Offshore /ˌɔːfˈʃɔːr/verb B2
When a company moves its work or factory to another country, usually to save money or find new customers.
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Operate /ˈɑpəreɪt/verb B1
To make something work or function; to use or run a machine or device.
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Oppose /əˈpoʊz/verb B1
To disagree with something; to try to stop or prevent something from happening.
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Optimize /ˈɒptɪmaɪz/verb B2
To make something work as well as possible by improving it. You optimize processes, costs, or performance to get the best results.
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Overcome /ˌoʊvərˈkʌm/verb B1
To succeed in handling something hard or beat a problem.
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Overdo /ˌoʊvərˈduː/verb B1
To do something too much or work too hard beyond what is necessary.
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Oversee /ˌoʊ.vərˈsiː/verb C1
to be responsible for checking that work is done correctly and properly managing people or tasks
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Obfuscate /əbˈfʌskeɪt/verb C2
To deliberately make something confusing or hard to understand on purpose. Often used when someone hides the truth or makes things unclear intentionally.
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Obstruct /əbˈstrʌkt/verb C1
To block something or prevent it from moving forward. Like putting something in the way.
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Onboard /ˌɒnˈbɔːrd/verb C1
To help a new employee learn how the company works, meet the team, and get ready to do their job. A company onboards new staff through training and orientation.
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Oscillate /ˈɑːsɪleɪt/verb C2
To swing or move back and forth in a regular pattern, like a pendulum. Can also mean to go back and forth between two ideas or positions.
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Ostracise /ˈɒstrəsaɪz/verb C2
To deliberately leave someone out or push them away from a group because they are not accepted or approved of.
See all 26 verbs that start with "O" →
Adjectives That Start With "O" (36)
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Obvious /ˈɒbviəs/adj A2
Easy to see or understand; not hidden or difficult.
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Ok /ˌoʊˈkeɪ/adj A1
Good enough; not bad, but not great.
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Old /oʊld/adj A1
Having been alive or existing for a long time.
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Open /ˈoʊpən/adj A1
Not covered or closed; you can go in or see inside.
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Original /əˈrɪdʒənəl/adj B1
The first version; something new and different from copies.
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Other /ˈʌðər/adj A1
Something different or extra from what you already have.
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Our /ˈaʊər/adj A1
Shows that something belongs to or is part of a group that includes you.
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Objective /əbˈdʒɛktɪv/adj B2
Using facts and evidence, not personal beliefs. An objective assessment considers only data, not emotions.
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Official /əˈfɪʃəl/adj A2
Approved by someone in power or authority.
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Online /ˌɑnˈlaɪn/adj B1
Working through the internet; available on computers.
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Opposite /ˈɑːpəzɪt/adj A1
Something that is totally different or on the other end of something.
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Optimal /ˈɒptɪməl/adj B2
Achieving the very best result or condition for a specific situation.
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Ordinary /ˈɔːrdəneri/adj A2
Usual or everyday; nothing unusual or special about it.
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Organic /ɔːrˈɡænɪk/adj B1
Food grown without artificial chemicals or harmful treatments; made the natural way without factory-made pesticides.
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Outdoor /ˈaʊtdɔːr/adj A2
Outside. Not inside a house or building. Happening in nature or fresh air.
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Overdue /ˌoʊvərˈduː/adj B1
Late; expected to arrive or be finished by now but has not happened yet.
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Overt /oʊˈvɜːrt/adj C2
Something that is open and honest, done in a way everyone can see. The opposite of hidden or secret.
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Obsolete /ˈɑːbsəliːt/adj C1
Old and no longer used because something newer has replaced it. Not fashionable or practical anymore.
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Occupational /ˌɒkjuˈpeɪʃənəl/adj C1
About the type of job someone has or the work they do every day. Related to their profession.
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Ongoing /ˈɑːnɡoʊɪŋ/adj B2
Something that is still happening now and continues to happen. Not yet finished or ended.
See all 36 adjectives that start with "O" →
Adverbs That Start With "O" (11)
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Off /ɔːf/adv A1
Not on; separated from something. Go away from.
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Only /ˈoʊnli/adv A1
Just this thing and nothing else; the single one among others.
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Out /aʊt/adv A1
Away from a place, building, or home; not inside.
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Obviously /ˈɒbviəsli/adv A2
In a way that is very clear or easy to understand.
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Often /ˈɔːfən/adv A1
Happening or done many times, not rarely.
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Once /wʌns/adv A1
A single time before; it happened one time in the past.
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Overall /ˌoʊvərˈɔl/adv B1
When you consider all the parts together or think about something as a complete picture.
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Originally /əˈrɪdʒənəli/adv B1
At the start or beginning; before any changes.
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Ostensibly /ɒˈstɛnsɪbli/adv C1
According to what seems true, though it might not actually be.
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Otherwise /ˈʌðərwaɪz/adv A2
In a different way, or showing what happens if you don't do something.
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Overseas /ˌoʊvərˈsiz/adv B2
In another country that is across the ocean. Going abroad or living in a foreign country far away.
How to Use Words That Start With "O"
Scrabble and Word Games
In Scrabble and Words With Friends, words starting with "O" can be valuable when you need to play through an existing tile on the board. Higher-tier letters like J, Q, X, and Z multiply your score quickly when stacked on bonus squares — scan the list below for short words that contain them. Two and three-letter words starting with "O" are especially useful for parallel plays where you build along an existing word and earn points for every adjacent tile.
Crossword Puzzles
For crossword puzzles, the most useful entries are mid-length common words — 5 to 8 letters — that fit standard grid patterns. Filter the list by length to match the cells in your clue. Pay attention to the CEFR level: clues from mainstream newspapers favour B1–B2 vocabulary, while themed and cryptic puzzles draw on rarer C1 and C2 words. The IPA shown on each card also helps confirm a guess — a clue marked "two syllables" should match a word with a simple stress pattern.
Creative Writing and Poetry
Writers and poets often look for groups of words starting with "O" to build alliteration, rhythm, or near-rhymes. Sort the list by length, scan the rare and C1+ words for fresh imagery, and use the linked dictionary entries to confirm connotation before you commit. The plain-English definitions are intentionally short so you can scan dozens of options without losing flow.
Longest Word That Start With "O"
Frequently Asked Questions About Words That Start With "O"
- How many words starting with "O"?
- There are 9,371 words starting with "O" in our 199,000-word English dictionary. The list ranges from common everyday words to rarer specialised vocabulary.
- What is the longest word starting with "O"?
- The longest word starting with "O" in our list is "OBJECTIFICATION" — 15 letters long. Tap the word to see its full definition.
- Are these words valid in Scrabble?
- Most of the words in this list are valid in Scrabble and similar word games (we cross-reference standard tournament dictionaries). A handful of proper nouns and very rare technical terms may not be — when in doubt, double-check with the official Scrabble dictionary used in your league.
- How many 5-letter words starting with "O"?
- 301 5-letter words starting with "O" — useful for Wordle, daily puzzles, and short crosswords. Filter by length above to see only 5-letter results.