Had an effect on each other or communicated and influenced one another.
From Latin 'inter' (between) + 'agere' (to act/do). The prefix 'inter-' means 'between' and 'action' comes from acting, so literally 'to act between.' The word became common in English in the 1950s-60s.
Before the 1960s, people didn't really use the word 'interact'—they just said people 'met' or 'talked'! The word became popular exactly when computers arrived, because scientists needed a term for how systems affected each other, and it stuck around.
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