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1530s, "a stretched condition," from Middle French tension, from Latin tensionem (nominative tensio) "a stretching" (in Medieval Latin "a struggle, contest"), noun of state from tensus, past participle of tendere "to stretch," from PIE root *ten- "stretch" (see tenet). The sense of "nervous strain" is first recorded 1763. The meaning "electromotive force" (in high-tension wires) is recorded from 1802.
tension ten·sion (těn'shən)
The act or process of stretching something tight.
The condition of so being stretched.
A force tending to stretch or elongate something.
The partial pressure of a gas, especially dissolved in a liquid such as blood.
Mental, emotional, or nervous strain.
Barely controlled hostility or a strained relationship between people or groups.