Trichotomy is the belief that man is made up of three parts - body, soul, and spirit.  While some believe the soul and spirit to be the same thing others maintain that it is different.  Paul writes in 1 Thessalonians 5:23 "May your whole spirit, soul, and body be kept blameless at the coming of our Lord Jesus Christ."

Likewise, Hebrews 4:12 speaks of the Word of God dividing the soul and spirit.

Others maintain that man is a dichotomy made up of body and soul.