Use 'internecine' when describing disputes that occur within a single group or organization, not between different ones. The board meeting turned internecine with trustees arguing fiercely among themselves.
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Negative Tone
'Internecine' has a negative connotation implying that the infighting is harmful to the group. The band's internecine squabbles eventually led to its breakup.
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Academic Context
Often found in scholarly texts, 'internecine' is formal and used in serious or historical discussions. The professor lectured on the internecine conflicts of the late Roman Republic.