One of a series of compounds that have the same molecular formula, that is, they contain exactly the same number of atoms of every element. The type of isomer can then be identified more precisely.
Structural isomers have the same molecular formula but different structural formulae.
4 H 10 but different structures. Stereoisomers even have the same structural formula but have a different orientation in space. For example, isomers related by cis-trans isomerism are stereoisomers as they differ only in the arrangement of the groups at each end of the double bond relative to each other. The New Penguin Dictionary of Science 2. The New Penguin Dictionary of Science 3.