counter-ion

American  

[koun-ter-ahy-uhn, -ahy-on] / ˈkaʊn tərˌaɪ ən, -ˌaɪ ɒn /

noun

Physical Chemistry.

1. an ion in solution that associates itself with an ion of opposite charge on the surface of a member of a solute.

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Etymology

Origin of counter-ion

counter- + ion