Not to mention
Definition 1 of 1
Pro Tip 1/3Adds Surprise
Use it when revealing information that is unexpected or adds impact. 
She's fluent in three languages, not to mention she's also a skilled violinist.
Pro Tip 2/3Additional Emphasis
It emphasizes an extra point that strengthens or supports what you've just said. 
The car is fast and stylish, not to mention it’s extremely fuel-efficient.
Pro Tip 3/3Somewhat Informal
It's casual, suitable for conversational context, rather than formal writing. 
He's got experience, not to mention a great sense of humor.