To infect is to spread germs, viruses, or harmful software into a person, animal, or system so that it becomes sick or damaged. It can also mean to spread an emotion or idea strongly to others.
It comes from Latin “inficere,” meaning “to stain,” “to dye,” or “to corrupt,” from “in-” (in) and “facere” (to make). The idea shifted from staining or tainting something to spreading disease.
Originally, to infect was to “stain” or “dye” something, which is a powerful image for how illness spreads through a body. Today we talk about “infected” computers and “infectious” laughter, showing how the idea expanded beyond medicine. The word always carries a sense of something unwanted sneaking in and taking over.
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