Some common words that start with O include obvious, optimistic, obscure, outstanding, obedient, objective, original, opportunistic, overwhelming, and obsessive.

Advanced words include obfuscate, omnipotent, ostentatious, obsequious, obstinate, opulent, oscillate, onerous, oblivious, and obtrusive.

Positive words include optimistic, outstanding, open-minded, obedient, objective, original, observant, outgoing, opportune, and open-hearted.

Negative words include obstinate, obnoxious, oppressive, obsessive, overly cautious, outdated, obscure, outlandish, obtuse, and ominous.

Here are some example sentences:

• She remained optimistic despite the challenges.
• His explanation was so obscure that no one understood it.
• The new policy had an onerous effect on employees.
• The mansion was opulent, decorated with gold and marble.

Synonyms: stubborn, inflexible, unyielding, headstrong, adamant

Antonyms: flexible, yielding, compliant, submissive, agreeable

To expand your vocabulary:

• Read books and articles that use diverse words.
• Use flashcards or vocabulary apps.
• Practice writing and speaking with new words.
• Play word games like Scrabble or crosswords.

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