The pair have been together since 2012 and have two children.
On Tuesday, the 50-year-old actor appeared on The Late Late Show With James Corden where the host asked Cannavale why he tends to refer to Byrne as his "wife."
"I haven't found a better word for it, to be honest. Boyfriend/girlfriend feels too young, partner feels too clinical," he said. "You know, my 'lady partner'? That feels weird. So it's just easier. People don't ask questions when you say, 'It's my wife.'"
Corden then joked of the titles, "I know what you mean about 'girlfriend,' although I do think if you and Rose stay together and you're in your 60s and 70s, then I think it's very cool to go back to calling each other 'girlfriend and boyfriend.' Then I think it comes back around."
"Imagine, I'll be 90 and she'll be like, 'This is my 90-year-old boyfriend,' by the way, 'Bobby.' You ever see a 90-year-old Bobby? It's hot!" Cannavale quipped.
Cannavale and the 41-year-old Australian actress share sons Rocco, 4, and Rafa, 3, and are notorious for keeping their personal life private. Cannavale was previously married to actress and screenwriter Jenny Lumet, with whom he shares 25-year-old son Jake.
Back in a 2017 interview with InStyle, Byrne did say of her longtime partner, "[Bobby] is one of a kind, man! He's endlessly interesting and entertaining. When something is special, it’s hard to articulate it, but I feel really lucky. We couldn't be from more different parts of the world, you know?"
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