sql syntax error

hi dears i have a trouble problem in my query, please help me thanks for helping."You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'deff_month month) as b from teacher_hours_late, teacher where teacher.teacher_' at line 1"

  $this->db->select("teacher.teacher_id,name,lname,father_name,salary_per_hour,monthly_salary,"
                        . "(select ($user_month - month(salary_start_date)) from teacher)as deff_month ,"
                        . "(select ADDDATE(salary_start_date, interval deff_month month) from teacher) as start_interval,"
                        . " (select ADDDATE(start_interval, interval 1 month)) as end_interval ,"
                        . "(select DATE_SUB(start_interval, interval 1 month)) as reverse_end_interval,"
                        . "(select date($miladi)) as user_date,(select sum(hours) from teacher_hours_late where (date>start_interval AND date<=end_interval AND start_interval<$miladi ) OR (date<=start_interval AND date>reverse_end_interval AND start_interval>=$miladi )) as total_late");
                $this->db->from('teacher');
                $this->db->join('teacher_hours_late',"teacher.teacher_id=teacher_hours_late.teacher_id", 'inner');

                $this->db->where('teacher.branch_id',$branch_id);
                $query=$this->db->get();
                return $query->result();