conium

As a noun corium

is (anatomy) the inner layer of skin, the dermis or corium can be (nuclear physics) the lavalike material produced in a nuclear meltdown.

As a proper noun conium is

.

As nouns the difference between conium and ionium

is that conium is any of one or two species in the genus Conium of poisonous perennial herbaceous flowering plants while ionium is a supposed decomposition-product of actinium once thought to be the source of radium.

As a noun onium

is (chemistry) any cation derived by the addition of a proton to the hydride of any element of the nitrogen, chalcogen or halogen families or onium can be (physics) the bound pair of a particle and its antiparticle.

As a proper noun conium is

.

As proper nouns the difference between cicuta and conium

is that cicuta is while conium is .