Negative adverb used before verbs, adjectives, and other adverbs to indicate negation; also used as a bound-form prefix to form terms with opposite meanings

(bound form) to share; to commonly possess; to partake in

(literary) To live in this world; literally "to have the sky above one's head". This is often used when expressing a deep-seated hatred that cannot be reconciled, as in 不共戴天 bù​gòng​dài​tiān