Obligatory Definition: Necessary, required or expected as a result of law or social custom. Synonyms: Necessary, Unavoidable, Needful, Imperative, Compulsory Antonyms: Desired, Willing, Voluntary, Self, Chosen

Oblivious Definition: The definition of oblivious is being forgetful or unaware of your surroundings. Synonyms: Forgetful, Absent – minded, Inattentive Antonyms: Attentive, Aware, Observant

Obvious Definition: The definition of obvious is something that is readily apparent or easy to see. Synonyms: Clear, Evident, Visible, Distinct, Palpable Antonyms: Hidden, Masked, Veiled, Covered, Secret

Obscure Definition: The definition of obscure is hard to see in the low light or hard to understand. Synonyms: Dark, Doubtful, Dim, Dense, Hidden Antonyms: Apparent, Intelligible, Lucid, Plain, Straightforward

Odd Definition: The definition of odd is different than the normal, not divisible by two or the one remaining when others are paired. Synonyms: Queer, Uneven, Uninvited, Irregular Antonyms: Usual, Match, Matching, Even, Parallel