Spirit & Soul, page-7

Definition: In the Bible, “soul” is translated from the Hebrew ne′phesh and the Greek psy·khe′. Bible usage shows the soul to be a person or an animal or the life that a person or an animal enjoys. To many persons, however, “soul” means the immaterial or spirit part of a human being that survives the death of the physical body. Others understand it to be the principle of life. But these latter views most commonly used are not Bible teachings.
This is where the confusion arises because of its most common usage being the same as one of the ways "spirit" is to be understood.
Definition: The Hebrew word ru′ach and the Greek pneu′ma, which are often translated “spirit,” have a number of meanings. All of them refer to that which is invisible to human sight and which gives evidence of force in motion. The Hebrew and Greek words are used with reference to (1) wind, (2) the active life-force in earthly creatures, (3) the impelling force that issues from a person’s figurative heart and that causes him to say and do things in a certain way, (4) inspired utterances originating with an invisible source, (5) spirit persons, and (6) God’s active force, or holy spirit.
That "soul"& "spirit" are different can be seen from Hebrews 4:12 which says:
" For the word of God is alive and exerts power and is sharper than any two-edged sword and pierces even to the dividing of soul and spirit, and of joints from the marrow, and is able to discern thoughts and intentions of the heart."