The IUPAC name for a benzene ring attached to another as a substituent is phenyl.

Here's why:

* Benzene is the base name for the six-membered aromatic ring.

* When benzene acts as a substituent (attached to another molecule), it loses the "-ene" ending and becomes phenyl.

For example, if a benzene ring is attached to a methane molecule, the compound would be called methylbenzene or toluene. In this case, "phenyl" is used to describe the benzene ring as a substituent on the methane molecule.