plural of octan

(astronomy) A small circumpolar constellation of the southern sky, said to resemble an octant. It lies closest to the southern celestial pole of any constellation.

A fever that recurs every eight days.

Occurring every eight days.

plural of octane

(organic chemistry) Any of the eighteen isomeric aliphatic hydrocarbons (C₈H₁₈) found in petroleum, especially an iso-octane 2,2,4 trimethyl-pentane; they are used as fuels and solvents.

(organic chemistry) The saturated aliphatic aldehyde having eight carbon atoms

(chemistry) Any isomer of octane except the normal, straight-chain one; especially 2,2,4-trimethylpentane.

(of fuel) Having a high octane number, good anti-knock characteristics; used in high performance vehicles. / (by extension) High powered, energetic, forceful or dynamic.

A measure of the antiknock properties of an automobile fuel; isooctane having an octane number of 100, a fuel with the same antiknock properties as a mixture of 90% isooctane and 10% heptane having an octane number of 90.