Ethene and Olefin

Ethene noun - A flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic.

Olefin and ethene are semantically related. In some cases you can use "Olefin" instead a noun "Ethene".

Olefin noun - Any unsaturated aliphatic hydrocarbon.

Ethene and olefin are semantically related. Sometimes you can replace term "Ethene" with "Olefin", this nouns are similar.