Simplify the following text for a Grade 11 native English-speaking person.
Original: Khan ( sometimes spelled Han , Xan , Ke-Han , Turkic : khÄ n , Chinese : å æ -- or å æ -- , kehan or dahan ) is an originally Central Asian title for a sovereign or military ruler , first used by medieval Altaic-speaking nomadic tribes living to the north of China .
Simplified: Khan ( sometimes spelled as Xan , Han , Ke-Han , Turkic : khÄ n , Chinese : å æ -- ) is an originally Central Asian title for a sovereign or military ruler .