Dictionary.net

Having the same percentage composition; -- said of two or more different substances which contain the same ingredients in the same proportions by weight, often used with with. Specif.: (a) Polymeric; i. e., having the same elements united in the same proportion by weight, but with different molecular weights; as, acetylene and benzine are isomeric (polymeric) with each other in this sense. See Polymeric. (b) Metameric; i. e., having the same elements united in the same proportions by weight, and with the same molecular weight, but which a different structure or arrangement of the ultimate parts; as, ethyl alcohol and methyl ether are isomeric (metameric) with each other in this sense. See Metameric.

Having the same percentage composition; - said of two or more different substances which contain the same ingredients in the same proportions by weight, often used with with. Specif.: (a) Polymeric; i. e.

Possessing isomerism.

Applied to compounds which are made up of the same elements in the same proportions, but having different properties.

ISOMERISM.

An epithet applied to different bodies which agree in composition, but differ in properties. The condition is termed Isomerism.

Made tip of the same elements in the same proportions, yet unlike.

Of chemical bodies, possessing the same number of atoms, but differing as regards the arrangement of the atoms in the molecule. [Gr.]