not to mention something

not to mention

In addition to or as well as what's been discussed. Typically used to mention an additional item when listing things that one considers negative. I've already got to spend three hours in the car running errands, not to mention the hour and a half it will take to pick up the kids from school. They have two massive houses in the city, not to mention their vacation home by the beach.See also: mention, not

not to mention something

used to introduce extra information and emphasize what you are saying: He’s got a house in London and a cottage in the country, not to mention the villa in Spain.See also: mention, not, something