Material cannot be deleted once any transaction is made against it.
If Item is newly created and no transaction is made against it then
1. Check if that item is not linked in Account Rule Definition (FARD)
If transactions are made against that item then
You can make that item inactive by following process
Once you make that material inactive, no more transaction can be made against it.
You can also make any master entry inactive through Inactive Master (UMMI).