Disagreement, conflict, or discord; to fail to agree or be in harmony with someone.
From dis- + accord (from Latin accordare, 'to bring into agreement'). The word accord itself came into English around 1300 and meant harmony; dis- inverts this to mean conflict.
While 'discord' means conflict, 'disaccord' adds a prefix that seems redundant—but in older English, both were used, and 'disaccord' emphasized the active breaking of an agreement or understanding.
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