The devil and satan

Human salvation depends upon the life, work and teaching of Jesus Christ.  We cannot understand this work unless we understand what the Bible means when the terms  DEVIL and SATAN are used.  The apostle John said,
“For this purpose the Son of God was manifested, that He might destroy  the  works of the devil” 1 John 3:8
Paul said that Jesus possessed human nature in order,
“that  through death  he  might destroy him that hath the power of death, that is, the devil” Hebrews 2:14

The devil

The New Testament was originally written in Greek and then translated into English.  The Greek word translated devil is diabolos  and its  meaning is slanderer or false accuser.  It is a compound word, dia which means "through" and ballo meaning "to strike or cast" and its literal meaning is "to strike through".  In the New Testament it has been translated in some places as "slanderer",
"Even so must their wives be grave, not slanderers (diabolos), sober, faithful in all things." 1 Timothy 3:11
However, on most occasions the translators transferred it into the script in an anglicised form of their own devising - as devil.  Yet in Titus they saw fit to translate it as “false accusers”,
“the aged women likewise, that they be in behaviour as becometh holiness, not false accusers” (diabolos).  Titus 2:3
If they had adhered to this rule all the way through the New Testament, much confusion and wrong ideas would have been avoided as the word itself has no connotation  to suggest an immortal evil being constantly tempting mankind.  Consider the two quotations  which follow which form an equation  thus -
“through death Christ destroyed him that had the power of death, that is the devil” Hebrews  2:14
and
“the sting (or power) of death is sin.” 1 Corinthians 15:56
Based on the above passages, the devil = sin, and was destroyed by Christ's death as Hebrews 2:14 says.  The devil is a personification of sin in human flesh.  This was what Christ destroyed.  How?  By voluntarily submitting to death and publicly demonstrating that human flesh was fit only for death as it was a  false accuser of God.  Also, by living a perfectly sinless life and suppressing every impulse to sin, though 
“in all points tempted like as we are, yet without sin” Hebrews 4:15
he declared God just in condemning sinful man to death.  This explanation of the word devil as  “sin  in  the flesh” agrees with all passages of scripture where the word occurs.  Sometimes scripture uses the term to describe the devil  (ie.  sin) within a human being and sometimes, the devil (ie. sin) without, in the form of governments as the Apostle Peter wrote,
“the devil, as a roaring lion, walketh about, seeking whom he may devour” 1 Peter 5:8
He refers here to the Roman power which persecuted  the early Christians.  In the gospel of  John, Christ, speaking of Judas, said,
“Have  not I chosen you twelve, and one of you is a devil?” John 6:70
It was Judas who falsely accused Christ  to  the rulers  of  the  Jews.
Sin and death are related as cause and effect.  If Christ came “to destroy him that had the power of death” then he came to take away sin.
“Behold the Lamb of God, that taketh away the sin of the world.”  John 1:29
"now once in the end of the world hath he (Jesus) appeared to put away sin by the sacrifice of himself." Hebrews 9:26

Sin brings death                                 

“By one man sin entered into the world, and death by sin”  Romans 5:12
Adam's disobedience to God's law brought upon him and on all his progeny (for like can only produce like) the punishment God had declared.
"But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die." Genesis 2:17
Adam, in believing the serpent rather than God, falsely accused God of  lying.  So the false accuser (the devil) or sin brought condemnation and death to man.   In contrast to Adam, Christ, by perfect obedience to all God's laws, 
“...our Saviour Jesus Christ, who hath abolished death, and hath brought life and immortality to light through the gospel." 2 Timothy 1:10
and destroyed  the  false  accuser.  

Satan

The word  satan,  like  the  word  devil,  has  not been translated.  It was originally a  Hebrew word, was then adopted into the Greek language and finally transferred to the English translation of both Old and New Testaments.  Had the word been translated, it would correctly have been  rendered “adversary” for this is its only meaning.  Indeed  there are places in the Old Testament where it has been so translated.  For example, 
“the  Lord stirred up an adversary (Hebrew satan)  unto Solomon” 1 Kings 11:14
Nowhere in the Old Testament is the word associated with a fallen  angel  or  any  kind  of supernatural agency. If, wherever the word occurs, the reader would translate it for himself as adversary, all difficulty  is removed, passages become clear and comprehensible and he will be correctly dealing with the Hebrew language.  This applies to both Old and New Testaments.  When Jesus warned his disciples that he must go to Jerusalem and there be put to death, Peter exclaimed, 
“Be it far from thee, Lord”. But Jesus  replied,  “Get thee behind  me, Satan (adversary): thou art an offence unto me.” Matthew 16:21-23 
Notice it was Peter himself who was acting as an adversary, standing in Christ's way, and trying to prevent him from fulfilling God's purpose.
In seeking to understand Bible teaching it is often helpful to look, with the aid of a good concordance, at the actual meaning of the Hebrew or Greek words in question, which have often, as we have seen in the case of  devil and satan, due to faulty translation, been the cause of misunderstanding God's revelation.