700 Words That Start With O (Mega List for Language Lovers)

Words / By /

Welcome to the ultimate guide to words that start with the letter O.

It doesn’t matter if you’re a word enthusiast, a parent looking for educational fun, or just someone who loves the English language, this mega list of 700 unique words beginning with O is sure to entertain and educate.

O Words for Kids

(This post may have afilliate links. Please see my full disclosure)
The Phrase WORDS THAT START WITH 0 with a smiley face on the O
I made this image with AI – Words That Start With O

Let’s start with some fun and easy words that kids will love to learn.

  1. Ocean
  2. Octopus
  3. Orange
  4. Owl
  5. Oven
  6. Olive
  7. Oink
  8. Oval
  9. Oasis
  10. Orca
  11. Ostrich
  12. Otter
  13. Orchard
  14. Oatmeal
  15. Onion
  16. Oxygen
  17. Ouch
  18. Omelet
  19. Organ
  20. Out
  21. Ox

Nice Words That Start With O

These pleasant words starting with O are sure to brighten your day.

  1. Optimistic
  2. Outstanding
  3. Original
  4. Open-hearted
  5. Outgoing
  6. Open-minded
  7. Organized
  8. Opulent
  9. Obliging
  10. Observant
  11. Opportunity
  12. Overflowing
  13. Ovation
  14. Oneness
  15. Orderly
  16. Objective
  17. Ornate
  18. Open-handed

Hard Words That Start With the Letter O

Ready to challenge your vocabulary? Try these tough O words.

  1. Obfuscate
  2. Obsequious
  3. Obstreperous
  4. Obliterate
  5. Ophthalmology
  6. Otorhinolaryngology
  7. Orthogonal
  8. Oscillate
  9. Obdurate
  10. Oleaginous
  11. Obeisance
  12. Obsolescence
  13. Obstetrician
  14. Ophiology
  15. Osmosis
  16. Oblation
  17. Obloquy
  18. Obsidian
  19. Odontology
  20. Onomatopoeia

Unique Words That Start with O

Stand out with these unique and interesting O words.

  1. Omnipotent
  2. Oxymoron
  3. Obelisk
  4. Omniscient
  5. Oscilloscope
  6. Oenology
  7. Obeah
  8. Ocarina
  9. Obcordate
  10. Oology
  11. Osmium
  12. Ornithology
  13. Oubliette
  14. Oxidize
  15. Oratorio
  16. Oblate
  17. Omphalos
  18. Oriel
  19. Oleander
  20. Orogeny

3-Letter Words That Start With O

Short and sweet, these three-letter O words are handy to know.

  1. Oak
  2. Oar
  3. Oat
  4. Odd
  5. Ode
  6. Off
  7. Ohm
  8. Oil
  9. Old
  10. One
  11. Orb
  12. Ore
  13. Our
  14. Out
  15. Obi
  16. Oaf
  17. Opt
  18. Ooh
  19. Ova
  20. Oxy

5-Letter Words That Start With O

Expand your vocabulary with these five-letter gems.

  1. Oaken
  2. Occur
  3. Offer
  4. Other
  5. Order
  6. Outer
  7. Owner
  8. Ounce
  9. Orbit
  10. Omega
  11. Ought
  12. Odder
  13. Opine
  14. Ovary
  15. Ozone
  16. Onset
  17. Opium
  18. Owlet
  19. Oxbow

Positive Words That Start With O

Spread positivity with these uplifting O words.

  1. Optimism
  2. Overcome
  3. Open
  4. Obedient
  5. Organize
  6. Opportunity
  7. Overflow
  8. Oomph
  9. Originality
  10. Obtain
  11. Onward
  12. Omnipresent
  13. Offer
  14. Ongoing
  15. Openhearted
  16. Overjoyed
  17. Optimist
  18. Opportune

Action Verbs That Start With the Letter O

Get moving with these action-packed O verbs.

  1. Observe
  2. Obstruct
  3. Obey
  4. Occupy
  5. Offset
  6. Operate
  7. Originate
  8. Overlook
  9. Override
  10. Oversee
  11. Overwrite
  12. Omit
  13. Oppose
  14. Optimize
  15. Obscure
  16. Obviate
  17. Obtain
  18. Officiate
  19. Orchestrate
  20. Overcome

Adjectives That Start With the Letter O

Describe the world with these O adjectives.

  1. Oblong
  2. Obvious
  3. Odd
  4. Official
  5. Old
  6. Open
  7. Onerous
  8. Optional
  9. Oral
  10. Organic
  11. Ornate
  12. Orthodox
  13. Obsolete
  14. Opaque
  15. Oval
  16. Overdue
  17. Overt
  18. Own
  19. Oily
  20. Omniscient

Animals That Start With the Letter O

Explore the animal kingdom with these O creatures.

  1. Okapi
  2. Orangutan
  3. Ocelot
  4. Opossum
  5. Oryx
  6. Osprey
  7. Onager
  8. Oyster
  9. Ostracod
  10. Olm
  11. Oilbird
  12. Orc
  13. Oystercatcher
  14. Oribi
  15. Oxpecker
  16. Ovenbird

Foods That Start With O

Feeling hungry? Check out these O foods.

  1. Oats
  2. Okra
  3. Oolong
  4. Oxtail
  5. Oregano
  6. Oatcake
  7. Olive oil
  8. Orange juice
  9. Ossobuco
  10. Oat milk
  11. Oeufs en meurette
  12. Opera cake
  13. Oblea
  14. Olallieberry
  15. Oyster sauce
  16. Okonomiyaki
  17. Orache
  18. Oshiruko
  19. Omelette

Scientific Terms That Start With O

Feed your curiosity with these scientific O terms.

  1. Orbit
  2. Organism
  3. Optics
  4. Ontology
  5. Oncology
  6. Orthopedics
  7. Orthogenesis
  8. Osmoregulation
  9. Oceanography
  10. Osteology
  11. Organogenesis
  12. Ophiolite
  13. Oceanology
  14. Oogenesis
  15. Osteoporosis
  16. Oligonucleotide
  17. Osmium
  18. Ozone
  19. Oxyacid

Words That Start With O and End With Letters A-Z

In this section, I will go over all the words that start with the letter O and end with one of the letters of the alphabet.

Words That Start With O and End With A

These O words wrap up with an A.

  1. Opera
  2. Omega
  3. Oceania
  4. Olea
  5. Ostia
  6. Onagra
  7. Orenda
  8. Ottava

Words That Start With O and End With B

There are not many words that start with O and end with B, but here are two.

  1. Ob
  2. Orb

Words That Start With O and End With C

These words start with O and end with C.

  1. Optic
  2. Orthopedic
  3. Obstetric
  4. Oceanic
  5. Odontic
  6. Orthorhombic
  7. Oxidic
  8. Ontologic

Words That Start With the Letter O and End With D

Let’s look at some O words ending with D.

  1. Overload
  2. Offered
  3. Obtained
  4. Observed
  5. Ordered
  6. Opened
  7. Overused
  8. Outdated
  9. Optimized
  10. Overheard
  11. Offload
  12. Outlived
  13. Overcrowded
  14. Outward
  15. Oxidized
  16. Overjoyed
  17. Outspread
  18. Outdid
  19. Outbred
  20. Overbred

Words That Start With the Letter O and End With E

These O words have an E at the end.

  1. Office
  2. Oblique
  3. Obscure
  4. Objective
  5. Observe
  6. Obsolete
  7. Opposite
  8. Operate
  9. Oracle
  10. Ozone
  11. Ordinate
  12. Originate
  13. Oxide
  14. Offense
  15. Overcome
  16. Oppose
  17. Oblige
  18. Oscillate
  19. Ovine

Words That Start With the Letter O and End With F

Here are some O words ending with F.

  1. Oaf
  2. Off
  3. Outf
  4. Orf (a viral disease in sheep)
  5. Overproof

Words That Start With O and End With G

Add these O words ending with G to your list.

  1. Operating
  2. Observing
  3. Offering
  4. Opening
  5. Organizing
  6. Outdoing
  7. Overtaking
  8. Overcoming
  9. Outliving
  10. Overhearing

Words That Start With the Letter O and End With H

These words start with O and end with H.

  1. Oomph
  2. Outreach
  3. Overshadow
  4. Overwash
  5. Overgrowth
  6. Outweigh
  7. Overstretch
  8. Oafish
  9. Oddish
  10. Offish

Words That Start With O and End With I

Exotic words ending with I.

  1. Obi
  2. Origami
  3. Oribi
  4. Oviri
  5. Onagri
  6. Omiai
  7. Ossi
  8. Otari

Words That Start With the Letter O and End With K

Check out these words I collected that start with the letter O and end with the letter K.

  1. Oak
  2. Outlook
  3. Overlook
  4. Outbreak
  5. Overwork
  6. Overcook
  7. Overspeak
  8. Overbook
  9. Overshock
  10. Outcrook

Words That Start With O and End With L

These O words end with L. How many do you know? How many are new words to you?

  1. Oatmeal
  2. Oral
  3. Oval
  4. Official
  5. Optional
  6. Occipital
  7. Opal
  8. Ordeal
  9. Overhaul
  10. Occidental

Words That Start With the Letter O and End With M

Let’s look at O words ending with M.

  1. Otium
  2. Organism
  3. Onium
  4. Opium
  5. Optimum
  6. Osmium
  7. Organum
  8. Ostium
  9. Occultism
  10. Optimism

Words That Start With O and End With N

Common O words ending with N.

  1. Option
  2. Oxygen
  3. Operation
  4. Organization
  5. Opinion
  6. Obligation
  7. Origin
  8. Occupation
  9. Observation
  10. Opposition
  11. Orphan
  12. Orientation
  13. Oscillation
  14. Overpopulation
  15. Oxidation
  16. Obsession
  17. Omission

Words That Start With O and End With O

These special words start and end with O.

  1. Onto
  2. Oratorio
  3. Olio
  4. Othello
  5. Outdo
  6. Outgo
  7. Overdo
  8. Orzo (removed duplicate from Foods)
  9. Octavo
  10. Oleo

Words That Start With the Letter O and End With R

These words end with R.

  1. Order
  2. Other
  3. Offer
  4. Owner
  5. Officer
  6. Observer
  7. Operator
  8. Organizer
  9. Originator
  10. Overseer

Words That Start With O and End With S

Plural words ending with S.

  1. Options
  2. Orders
  3. Objects
  4. Offices
  5. Opportunities
  6. Operations
  7. Organizations
  8. Opinions
  9. Observations
  10. Owners

Words That Start With the Letter O and End With T

Here are O words that that end with T.

  1. Out
  2. Object
  3. Obstruct
  4. Occult
  5. Octet
  6. Offbeat
  7. Outfit
  8. Outright
  9. Oversight
  10. Overreact

Words That Start With the Letter O and End With W

Don’t skip these O words that end on the letter W.

  1. Outlaw
  2. Overdraw
  3. Oversaw
  4. Overview

Words That Start With the Letter O and End With Y

We are almost to the end now with these O words that end with the letter Y.

  1. Obesity
  2. Obituary
  3. Objectify
  4. Obloquy
  5. Odyssey
  6. Oily
  7. Oligarchy
  8. Ontology

Additional O Words

Let’s add even more words to complete our mega list.

  1. Obdurate
  2. Obedience
  3. Obelisk
  4. Objector
  5. Oblation
  6. Obligee
  7. Oblong
  8. Obnoxious
  9. Obscene
  10. Observant
  11. Obsess
  12. Obstacle
  13. Obstinate
  14. Obtrude
  15. Obverse
  16. Obviate
  17. Occasional
  18. Occasion
  19. Occiput
  20. Occlude
  21. Occlusion
  22. Occupant
  23. Oceanic
  24. Octagon
  25. Octal
  26. Octane
  27. Octant
  28. Octave
  29. October
  30. Octogenarian
  31. Ocular
  32. Odious
  33. Odin
  34. Odor
  35. Offense
  36. Officiate
  37. Officious
  38. Offshore
  39. Ogle
  40. Oilcloth
  41. Oilskin
  42. Ointment
  43. Ojibwa
  44. Okenite
  45. Olden
  46. Oldie
  47. Oleic
  48. Oleomargarine
  49. Oligocene
  50. Olympic
  51. Omen
  52. Ominous
  53. Omnibus
  54. Omnivore
  55. Onlooker
  56. Online
  57. Onrush
  58. Onward
  59. Oodles
  60. Oolite
  61. Opine
  62. Opponent
  63. Oppress
  64. Optical
  65. Optician
  66. Oracle
  67. Orate
  68. Orbit
  69. Orchestra
  70. Orchid
  71. Ordain
  72. Ordeal
  73. Ordinary
  74. Ordinal
  75. Ordinance
  76. Ordure
  77. Organ
  78. Organic
  79. Orient
  80. Oriental
  81. Original
  82. Oriole
  83. Ornament
  84. Orthodox
  85. Orthodontist
  86. Ossify
  87. Ossuary
  88. Osteopath
  89. Osteopathy
  90. Ostracize
  91. Otherwise
  92. Ought
  93. Ounce
  94. Outage
  95. Outback
  96. Outbid
  97. Outcome
  98. Outdoor
  99. Outfield
  100. Outlet
  101. Outline
  102. Outlook
  103. Output
  104. Outrage
  105. Outsell
  106. Outside
  107. Outsider
  108. Outskirts
  109. Outspoken
  110. Outwit
  111. Overall
  112. Overact
  113. Overcast
  114. Overcharge
  115. Overcook
  116. Overcrowd
  117. Overdo
  118. Overdose
  119. Overeat
  120. Overhead
  121. Overhear
  122. Overjoy
  123. Overkill
  124. Overlap
  125. Overlay
  126. Overpay
  127. Overpower
  128. Overrate
  129. Overrun
  130. Overshoot
  131. Overt
  132. Overture
  133. Overturn
  134. Ovulate
  135. Ovum
  136. Owe
  137. Ox
  138. Oxen
  139. Oxidant
  140. Oyer
  141. Oyez
  142. Obbligato
  143. Obsolescent
  144. Outmaneuver
  145. Overexert
  146. Overindulge
  147. Overwhelm
  148. Outperform
  149. Outplay
  150. Outpouring
  151. Outrank
  152. Outrageous
  153. Outrun
  154. Outshine
  155. Outstretch
  156. Outstrip
  157. Outsmart
  158. Overabundance
  159. Overachieve
  160. Overambitious
  161. Overanalyze
  162. Overbearing
  163. Overboard
  164. Overburden
  165. Overcareful
  166. Overconfident
  167. Overcritical
  168. Overdevelop
  169. Overdone
  170. Overdrawn
  171. Overdrive
  172. Overemphasize
  173. Overenthusiastic
  174. Overestimate
  175. Overexcited
  176. Overexpose
  177. Overextend
  178. Overfull
  179. Overgeneralize
  180. Overhasty
  181. Overlie
  182. Overlong
  183. Overly
  184. Oviform
  185. Oviparous
  186. Ovoviviparous
  187. Ovoid
  188. Oxyacetylene
  189. Oxygenate
  190. Oxymel
  191. Oxytone
  192. Ozonize
  193. Ozonosphere
  194. Ozonize
  195. Ozonide
  196. Obole
  197. Obovate
  198. Obscurant
  199. Obsequies
  200. Obstetrics
  201. Obtest
  202. Obturate
  203. Ocotillo
  204. Ocrea
  205. Octachord
  206. Octillion
  207. Octopod
  208. Octosyllable
  209. Odograph
  210. Odoriferous
  211. Oecology
  212. Oersted
  213. Oestrus
  214. Offal
  215. Offprint
  216. Offscouring
  217. Ogive
  218. Oleaster
  219. Oleograph
  220. Oleoresin
  221. Oleum
  222. Olibanum
  223. Oligarch
  224. Oologist
  225. Obcordate
  226. Obelize
  227. Obfuscation
  228. Oblanceolate
  229. Obnubilate
  230. Obsecrate
  231. Obsequy
  232. Obstipation
  233. Oblation
  234. Obtestation
  235. Obtrusive
  236. Obumbrate
  237. Obvolute
  238. Occident
  239. Occidentalism
  240. Occultist
  241. Oceanarium
  242. Oceangoing
  243. Ochlocracy
  244. Octillion
  245. Odalisque
  246. Odontalgia
  247. Odontoblast
  248. Odorless
  249. Oenomel
  250. Oenophile
  251. Offertory
  252. Oleaceous
  253. Oligoclase
  254. Ophiology
  255. Obliquity
  256. Oligotrophic
  257. Omnibenevolent
  258. Oleiculture

Here is a cute video for kids about words that start with the letter O:

YouTube Video by 123ABCtv — Words That Start With the Letter O

How to Use Words That Start With the Letter O

Whether you’re a teacher, a student, or a language enthusiast, there are numerous ways to incorporate these O words into your learning and teaching practices.

Here’s how you can make the most out of this extensive list.

Teachers

Teachers can use this list as a valuable resource to enhance vocabulary lessons and engage students in interactive activities.

  • Vocabulary Building: Introduce a new O word each day to expand your students’ vocabulary.
  • Spelling Bees: Organize spelling competitions using words from different difficulty levels.
  • Creative Writing Prompts: Encourage students to write stories or essays incorporating a set number of O words.
  • Word Games: Use the list for games like Hangman, Scrabble, or word searches to make learning fun.
  • Thematic Lessons: Design lesson plans around specific categories like animals, foods, or scientific terms starting with O.

Students

Students can leverage this list to improve their language skills and make learning more enjoyable.

  • Self-Study: Pick a few words each week to learn their meanings and use them in sentences.
  • Enhance Writing: Use unique and hard O words to enrich essays and creative writing assignments.
  • Test Preparation: Study these words to prepare for vocabulary tests, SATs, or spelling bees.
  • Peer Learning: Team up with classmates to quiz each other on definitions and spellings.
  • Language Games: Challenge yourself with crosswords or word puzzles using these O words.

General Language Learners

For anyone looking to broaden their English vocabulary, this list offers a wealth of opportunities.

  • Daily Vocabulary Expansion: Learn a new word every day to steadily enhance your vocabulary.
  • Conversation Skills: Incorporate positive and nice O words into your daily conversations.
  • Language Apps: Input these words into language learning apps to practice and memorize them.
  • Cultural Exploration: Delve into words from different categories to learn about various fields like science, art, and cuisine.
  • Personal Challenges: Set goals to use a certain number of new O words each week in writing or speech.

Fun Facts About Words That Start With the Letter O

Here are some fun facts about words that start with the letter O:

here are 10 fun facts that highlight some of the most interesting aspects of words starting with the letter O.

  1. Longest O Word: The longest word starting with O in the English language is “otorhinolaryngological,” which has 22 letters. It pertains to the medical specialty dealing with the ear, nose, and throat.
  2. Shortest O Words: There are several two-letter words starting with O, including “ob,” “od,” “oe,” “of,” “oh,” “oi,” “om,” “on,” “op,” “or,” “os,” “ow,” and “ox.” These are useful in word games like Scrabble.
  3. Palindromic O Word: The word “otto” is a palindrome, meaning it reads the same backward and forward.
  4. Contronym O Word: The word “oversight” is a contronym—it has two opposite meanings: it can mean supervision or an unintentional failure to notice something.
  5. Most Common O Word: The word “of” is one of the most frequently used words in the English language, essential in constructing sentences.
  6. Unusual Plurals: The plural of “ox” is “oxen,” which is one of the few English words to form the plural with -en instead of the standard -s or -es.
  7. Words Borrowed from Japanese: The word “origami” is borrowed from Japanese and refers to the art of paper folding.
  8. Words with Double O’s: Words like “ooze,” “oops,” and “oodles” start with double O’s, creating unique sounds and spellings.
  9. Scientific Words: Many scientific terms start with O, such as “osmosis,” the process by which molecules pass through a semipermeable membrane, and “oxidation,” a chemical reaction involving the loss of electrons.
  10. Oldest English Words Starting with O: Words like “one,” “out,” and “over” are among the oldest in the English language, tracing back to Old English and even Proto-Indo-European roots.

Final Thoughts: Words That Start With the Letter O

I hope you’ve enjoyed this mega guide to words that start with O.

If you’re into words as much as I am, you’re going to love all the other blog posts about letters. Check out the list I’ve hand-selected below.

Read This Next: