How do i delete a git branch?

[giraffelife]

git man page: http://bit.ly/2nvGNWB

To delete a branch run the following, without having it checked out, i.e you cannot be in the branch you are deleting.

$ git branch -d new_dev
error: Cannot delete the branch 'new_dev' which you are currently on.

$ git checkout dev
Switched to branch 'dev'
$ git branch -d new_dev
Deleted branch new_dev (was 5dde774).