Question

What are alkenes that contain two double bonds called?

Answer 1

They are called dienes.

Explanation:

The suffix (-ene) is used for alkenes, which means there is at least one C=C bond. The general term for alkenes with more than one C=C bond is polyene. The general term specifically for two C=C bonds is diene.

The structural formula below represents the simplest diene, `"C"_3"H"_4"`. It's systematic name is propa-1,2-diene and is also called allene.

https://en.wikipedia.org/wiki/Propadiene
https://pubchem.ncbi.nlm.nih.gov/compound/Allene#section=3D-Conformer