Cis

In chemistry, a double bond in which the greater radical on both ends is on the same side of the bond is called cis. See trans[?].

This comes from a Latin word meaning "on the same side". See Ciskei[?] and Transkei, also Cisalpine Gaul[?] and Transalpine Gaul[?].

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In mathematics, e^ix = cos x + i sin x. This is abbreviated cis x.