Never mind is used when you want to tell someone not to be worry about something, as it's insignificant.

"Never mind" means "forget about it" or "don't worry about it." "Nevermind" is also an album by Nirvana. For example: "Are you going to the party tonight?" "What?" "Are you going to the party?" "I can't understand you." "I said are you... oh, never mind..."

It is used to tell someone not to worry about something because it is not important. for example: A : Oh I am sorry I lost that picture you gave me! B: Never mind, I can easily give you another one.

The expression "nevermind" was invented 1976 by two women, Miss Emily Litella and Roseanne Roseannadanna. Here is Miss Emily talking about a problem on the nightly news, during which she demonstrates how nevermind should be used. It should be obvious that nevermind is one word, not two: http://www.nbc.com/saturday-night-live/video/emilys-editorial-reply/n8635 Sadly, both Miss Emily and Roseanne Roseannadanna passed away in 1989. They made the expression "nevermind" famous, and no-one has used it nearly as well since. P.S. Watch the video before reading the sidebar.

En español = no te preocupes or no importa In English we use it mostly to dismiss an idea or to tell someone that you don't want to talk to someone. ex. "Sandra, I know you wanted McDonalds but there isn't one close by. Would you like Burger King instead?" "Nevermind, I'll just find something at home to eat."