30 Most Useful Adjectives That Start with O for English Learners

We don’t mean to be over-exaggerated, yet we are optimistic that this is obviously the world’s most outstanding list of adjectives that start with O! These O adjectives can be utilized when you are playing a game, defining an individual, praising a person, writing a book, a social post or merely increasing your vocabulary.

There are hundreds of O adjectives in the English language and it is hard to list all of them in a single article. Therefore we carefully selected the most useful adjectives that start with O by Greenopolis. We hope you find it helpful in your daily life and can find the exact adjectives beginning with O that you’ve been looking for.

1. Obvious

Definition: easy to see, recognize, or understand

Example: They have a small child so for obvious reasons they need money.

2. Occupied

Definition: being used by someone; with someone in it

Example: The bathroom at the back of the plane was occupied, so I waited.

3. Old

Definition: having lived or existed for many years

Example: Now come on, you’re old enough to tie your own shoelaces, Carlos.

4. Overweight

Definition: too heavy or too fat

Example: He’s at least 20 pounds overweight.

5. Only

Definition: used to show that there is a single one or very few of something, or that there are no others

Example: The only thing that matters is that the baby is healthy.

6. Open

Definition: not closed or fastened

Example: An open suitcase lay on her bed.

7. Operational

Definition: (of machinery, devices, or processes) ready to work correctly

Example: Repairs have already begun and we expect the plant to soon be fully operational.

8. Opposed

Definition: completely different

Example: His view of the situation is diametrically opposed to mine.

9. Opposite

Definition: being in a position on the other side; facing

Example: The map on the opposite page shows where these birds commonly breed.

10. Optional

Definition: If something is optional, you can choose if you want to do it, pay it, buy it, etc.

Example: English is compulsory for all students, but art and music are optional.

11. Optimal

Definition: the best or most effective possible in a particular situation

Example: Companies benefit from the optimal use of their resources and personnel.

12. Oral

Definition: spoken and not written

Example: Only in borderline cases will pupils have an oral exam.

13. Ordinary

Definition: not different or special or unexpected in any way; usual

Example: Readers of the magazine said they wanted more stories about ordinary people and fewer stories about the rich and famous.

14. Orange

Definition: of a colour between red and yellow

Example: The setting sun filled the sky with a deep orange glow.

15. Organic

Definition: not using artificial chemicals in the growing of plants and animals for food and other products

Example: These organic olives are packaged in recycled glass containers.

16. Other

Definition: as well as the thing or person already mentioned

Example: There is only one other person who could help us.

17. Original

Definition: existing since the beginning, or being the earliest form of something

Example: The gardens have recently been restored to their original glory.

18. Outgoing

Definition: (of a person) friendly and energetic and finding it easy and enjoyable to be with others

Example: Sales reps need to be outgoing, because they are constantly meeting customers.

19. Organizational

Definition: relating to the planning of an activity or event

Example: She is looking for a personal assistant with good organizational skills.

20. Outrageous

Definition: shocking and morally unacceptable

Example: The judge criticized the “outrageous greed” of some of the bankers.

21. Outside

Definition: coming from another place or organization

Example: The company has called in outside experts.

22. Outstanding

Definition: clearly very much better than what is usual

Example: It’s an area of outstanding natural beauty.

23. Overall

Definition: including all the people or things in a particular group or situation

Example: The overall situation is good, despite a few minor problems.

24. Oblique

Definition: having a sloping direction, angle, or position

Example: Through the window came the last few oblique rays of evening sunshine.

25. Own

Definition: belonging to or done by a particular person or thing

Example: You’ll have to fix your own dinner.

26. Obedient

Definition: doing, or willing to do, what you have been told to do by someone in authority

Example: Students are expected to be quiet and obedient in the classroom.

27. Objective

Definition: based on real facts and not influenced by personal beliefs or feelings

Example: I can’t really be objective when I’m judging my daughter’s work.

28. Obliging

Definition: willing or eager to help

Example: He found an obliging doctor who gave him the drugs he needed.

29. Obscure

Definition: not clear and difficult to understand or see

Example: Official policy has changed, for reasons that remain obscure.

30. Offensive

Definition: causing offence

Example: He told some really offensive sexist jokes.

This collection of adjectives beginning with O was very carefully chosen to provide you with the most useful possible list that contains all of those which might really be used in daily life or are common in writings, while not containing those that are so rarely used that they would be meaningless to include to this list.

There are some adjectives starting with O to describe a person in the list that would certainly be ideal for compliments or to be used in greeting cards to loved ones. For example, a person can be optimistic, omnipotent, outgoing, outstanding and more. Of course, there are some adjectives that start with O carry negative connotations as well. So whenever you need O adjectives, don’t hesitate to come back and check again!