conflict

Etymology

From Latin conflictus, past participle of confligere (“to strike together”), from com- (“together”) (a form of con-) + fligere (“to strike”).

noun

1. A clash or disagreement, often violent, between two or more opposing groups or individuals.
   The conflict between the government and the rebels began three years ago.
   One particularly damaging, but often ignored, effect of conflict on education is the proliferation of attacks on schools[…]as children, teachers or school buildings become the targets of attacks. Parents fear sending their children to school. Girls are particularly vulnerable to sexual violence. 2013-07-19, Mark Tran, “Denied an education by war”, in The Guardian Weekly, volume 189, number 6, page 1
2. An incompatibility, as of two things that cannot be simultaneously fulfilled.
   I wanted to attend the meeting but there's a conflict in my schedule that day.

verb

1. (intransitive) To be at odds (with); to disagree or be incompatible
   [T. E.] Lawrence said that in the end he felt himself to be fighting not for the imperial British but for the rebellious Arabs. All too often he conflicted with British bureaucratic fustiness. 2 March 2014, Jan Morris, “Lawrence in Arabia: War, Deceit, Imperial Folly and the Making of the Modern Middle East by Scott Anderson, review: A skilful account of T. E. Lawrence and his role in the painful birth of an emerging Middle East [print version: A rock in Arabia's shifting sands, 1 March 2014, p. R26]”, in The Daily Telegraph (Review)
2. (intransitive) To overlap (with), as in a schedule.
   Your conference call conflicts with my older one: please reschedule.
   It appears that our schedules conflict.