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cis-

On this side of; on the side nearer the speaker.

Latin cis, on this side of.

The adjective cisalpine refers to the southern side of the Alps (from the perspective of Rome, since the Romans invented the term); cisatlantic refers to the speaker's side of the Atlantic; something cismontane is on this side of the mountain; cislunar means this side of the Moon, between the Earth and the Moon.

The form also indicates isomers of chemical compounds in which substituents at opposite ends of a carbon-carbon double bond are on the same side of the bond, as in cisplatin, an anti-tumour drug, or in formal chemical names such as cis—2—butene. Its opposite is trans‑.

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