What's the "een" in Halloween?
isomerism i·som·er·ism (ī-sŏm'ə-rĭz'əm)
The phenomenon of the existence of isomers.
The complex of chemical and physical phenomena characteristic of or attributable to isomers.
The state or condition of being an isomer.
structural isomerism n.
Isomerism involving the same atoms in different arrangements.