the.com/enemy

Someone whose failure you'd mourn less than your own dinner going cold.

means A person actively opposed to or hostile toward you, working against your interests rather than merely disliking you in passing.

from From Old French 'enemi', from Latin 'inimicus' — literally 'not-friend', built from 'in-' (not) plus 'amicus' (friend, related to 'amare', to love). So an enemy is, at the etymological root, simply the negation of love — the word doesn't invent hatred so much as it erases friendship and leaves the cold shape behind.

etymology
Latin inimicus, literally not-friend
psychology
brain treats them as subhuman to ease guilt
sun tzu rule
know them better than yourself
irony
often created by mere proximity, not hatred
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