A Field can not be deleted,it can be made inactive by Inactive option.To access the option, the user has two alternative options. User can either select field by left click of the mouse button. The Inactive option is then listed as buttons on top of the list control.
User can also right click on the Field and Inactive option is then listed as the context menu.
If a field is made inactive then it will go to the inactive list.And we can view the inactive list of fields by selecting Inactive option from the drop down list at the right side corner of the page.