Article: Often categorised with the New Wave of British Heavy Metal, in 1981 Def Leppard released their second album High 'n' Dry, mixing glam-rock with heavy metal, and helping to define the sound of hard rock for the decade. The follow-up Pyromania (1983), reached number two on the American charts and the singles "Photograph", "Rock of Ages" and "Foolin'", helped by the emergence of MTV, all reached the Top 40. It was widely emulated, particularly by the emerging Californian glam metal scene. This was followed by US acts like Mötley Crüe, with their albums Too Fast for Love (1981) and Shout at the Devil (1983) and, as the style grew, the arrival of bands such as Ratt, White Lion, Twisted Sister and Quiet Riot. Quiet Riot's album Metal Health (1983) was the first glam metal album, and arguably the first heavy metal album of any kind, to reach number one in the Billboard music charts and helped open the doors for mainstream success by subsequent bands.

Now answer this question: What sub-genre of hard rock does Def Leppard belong to?
the New Wave of British Heavy Metal