THIS PAGE (Part I)
What Is Sin?
Anyone who does not view sin as God views it is making a gargantuan mistake. Most people consider themselves 'good people' by the generally accepted ideas as to what constitutes respectable behavior. However. although their lives and conduct may meet the world's approval it may fall very short when it comes to the benchmark set by the Bible.
Why It Is So Important To Understand How The Bible Defines Sin
The consequences are severe and permanent. ALL sin carries the death penalty. Life, both symbolically and physically, is in the blood. Therefore the penalty for sin is the shedding of blood - yours.
Imagining A World Without Sin
What would it be like to never have to worry about the safety of our children, and never have to lock the doors to our homes or worry about terrorists, or the unrestrained greed that marks most of the world's businesses.
A Severe Warning - Hebrews 10:26-31
In chapter 10 the author of the book of Hebrews warned Jewish Christians who were contemplating returning to Judaism about what an unimaginably serious step they were considering.
NEXT PAGE (Part II)
Greater and Lesser Sins, Unintentional Transgressions and Sins of Omission. Presumptuous, Intentional, or Deliberate Sin. The Letter Vs. The Spirit of The Law. The Atonement for Sin, Iniquity and Transgression. The Believer's Predicament - The Battle Between Flesh and Spirit.
What Is Sin?
From the beginning of time, virtually every ethnic group in the world has held on to their own unique set of beliefs that helped them cope with the issues of life and death and, more often than not, they also practiced some form of appeasement of the gods. These acts of conciliation including food or flower offerings, personal penance, animal sacrifices etc. The most gruesome involved the ritual human sacrifices of the Aztec, Mayan and Incan civilizations and the child sacrifices of the ancient Canaanites. Even some of the worst of the Roman emperors felt the need to propitiate the gods.
In other words, humans often instinctively sensed that they were accountable to a "higher being". Either they felt that had not done what that being required or expected of them and the offering was 'fire insurance' - or they had a request to make. Even today people are often instinctively aware of an invisible benchmark that keeps them from doing something inappropriate, improper, or even illegal.
On the other hand, the very concept of "sin" seems to some to be nothing but remnants of rather simplistic and naive religious beliefs.
... an arrogant imposition of 'religion' — an invention of the priest craft and clergy for the purpose of exercising control over the masses. Others will pontificate that 'sin' is simply an ignorant appellation for those cultural and psychological aberrations which plague our society. 
Our Opinions Vs. God's View
Not only is the word "sin" becoming increasingly obsolete - but how it is defined varies from group to group, or even from person to person. According to a survey conducted by Ellison Research in Phoenix, adultery (81%) and racism (74%) top the list of what people consider sins. However, only 45% call premarital sex a sin, while 30% say gambling is sinful. 
Many today say that they try to live their lives by some form of the Golden Rule, i.e. we treat others exactly as we ourselves would wish to be treated in the same situation. If pressed,
The majority of people in the western world would probably place themselves in the 'not perfect' category, but a far cry from 'sinners' or really bad people, usually defined as the serial killers, rapists and child molesters of the world.
Others believe that even if there is a God against whom we sin, He is too "loving" to actually hold our 'mistakes' against us, much less punish us for them.
However, perhaps the most common belief is the almost universal 'Santa Claus' mentality of rewards for those who's good deeds outweigh the bad, and punishment for those for whom the opposite is true. When we die, our good deeds and our bad deeds will be weighed on a pair of divine scales to determine whether we will spend eternity balancing on a fluffy cloud and strumming a harp, or in a blistering cauldron being constantly poked by someone in a red suit and horns.
Even those that believe in a higher power tend to have extremely diverse opinions regarding sin and its consequences. Considering the place of honor the Ten Commandments often occupy on the walls of our courtrooms, school rooms, and churches, I suspect the vast majority believe that these are basic rules by which all of us are to live. In fact, But is this true? Since this is a subject too detailed to cover here, See Jesus and The Law.
In summary, God and His word are no longer the yardstick by which sin is determined and measured. As said by Albert Mohler
Even some people who say sin is real still steer by a compass of "moral pragmatics," not a bright line of absolute truth, Mohler says. "People say, I have high moral expectations of myself and others, but I know we are all human so I'm looking for a batting average.’
We find a comfort zone of morality, a kind of middle-class middle level where we think we are doing well. We cut the grass. We don't double-park. But we ignore the larger issues of sin.
Instead of violating the law of the Creator, it becomes more a matter of etiquette. … We want our kids to play well in the sandbox and know their place in line. We want people to do things decently and in order... 
The problem is that none of these views come anywhere near agreeing with the Biblical definition of sin, judgment, or even heaven and hell. Links to What and Where is Heaven? and What and Where is Hell? Below
Why It Is So Important To Understand How The Bible Defines Sin
The Consequences of Sin
The twin subjects of sin and salvation are the warp and weft of the fabric the Bible is woven out of which should tell us how crucially important the subject are. Perhaps something the prophet Isaiah said should give us a clue. In his words ... "... your iniquities have separated you and your God; and your sins have hidden His face from you, so that He will not hear" (Isaiah 59:2).
Paul was even more blunt stating "For the wages of sin is death (Gr. thanatos) ... " (Romans 6:23)
(Please Note: thanatos means a literal death, not eternal life in hell. See Those Overlooked Greek Words T
In other words, ALL sin carries the death penalty. The animal sacrifices of the Old Testament were a vivid reminder that God demanded death as a punishment for every wrongdoing. Because atonement for sin is only made by shedding of blood, the animal functioned as a substitute for the offender, and bore the punishment of the person who had sinned.
The consequences of sin have not changed since Old Testament days - you sin... you die! The only difference is that justice is not immediate like it used to be. But nonetheless it is certain. However, whether we pay the ultimate price for our sins or whether we obtain forgiveness for them is up to us. God in His infinite mercy sent His Son to pay the price for us. As the ancient prophet wrote
... He was pierced through for our transgressions (Heb. pesha), He was crushed for our iniquities (Heb. âvôn); The chastening for our well-being fell upon Him, And by His scourging we are healed. (Isaiah 53:5 NASB) See Salvation
Note. Unfortunately, verses like Isaiah 53:5, John 1:29, Romans 5:18 etc, have sometimes been taken to mean that Christ's death on the cross provides atonement for sin and redemption for all humanity. This regardless of whether they have repented of their sins, trusted in Christ for salvation etc. Unfortunately this belief can be assigned to the wishful thinking category. See Universalism
If you think the Bible seems too harsh when it says that all sin merits death, You need for a few moments to envision a world without sin - without transgression of God's laws which, by the way, is God's plan for the world .. also called Heaven.
Imagining A World Without Sin
What would it be like to never have to worry about the safety of our children, and never have to lock the doors to our homes or cars. A young woman could walk home late in the evening and know she would get there safely. Pornography would not exist. There would have been no Enron and no Watergate. What would it be like if politicians and used car salesmen told nothing but the truth? Children would be raised in the security of two parents who are committed to one another.
While there is little doubt that some crimes arise out of need and desperation, the vast amounts of funds we would save on our police force, judiciary, armed forces and related organizations would ensure that no one would be in want.
Are we getting the picture yet?
Perhaps the Bible has a point after all.
But how can a tiny infraction deserve death? Lets look at it this way...
Where does one draw the line between a 'big' sin and a 'small' one? If I as a 'friend' of yours, walked away with a paper clip from your desk you probably would not consider it theft. If you thought about it at all, you would probably conclude that I needed a paper clip for some reason and dismiss it. If I walked away with a five-dollar bill you would probably look askance at me but may look the other way. However if I actually walked away with $100 you would probably jump up and down.
So where shall we draw the line between a paper clip and a hundred dollar bill? At a penny? A dime? A nice pen? A tenner?
And how much are you willing to bet that, if asked, ten people would give ten different answers. And how much more would you be willing to bet that (sooner, rather than later) some one will eventually come to the conclusion that the thief is a victim of social / cultural/psychological circumstances and should see a psychologist, instead of being punished.
Back to square one. Besides which, cultures and people across the globe have different standards.… So whose standard shall we judge by?
God made it simple. He set the standard... He said "no sin".
Also See What is Holiness - Past 2 of Holiness
The Bible says "Without Holiness, No Man Shall See God!" (Hebrews 12:14) in view of which perhaps it would be wise to know exactly what it means by holiness. The problem is that in the 21st century the word "Holy" often coveys some very negative connotations - used to describe someone who is self-righteous, smug, sanctimonious, goody-goody, priggish etc. Even to most Christians, the word "holy" implies moral goodness. However, this is only part of the meaning.
A Severe Warning - Hebrews 10:26-31
For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, but a terrifying expectation of judgment and the fury of a fire which will consume the adversaries. Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses. How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace? For we know Him who said, "vengeance is mine, I will repay." and again, "the Lord will judge His people." It is a terrifying thing to fall into the hands of the living God. (Hebrews 10:26-31 NASB)
Like Hebrews 6:4-6 this passage has given rise to considerable differences of opinion. However, that the believer who turns his back of Christ only has judgment to look forward to fits in perfectly with the general tone and aim of Hebrews that can be summed up by four words - The Superiority of Christ. The book can be divided into sections, each of which details Jesus' superiority over various ancients, the temple sacrifices, and the Old Testament covenant itself.
Each section also usually includes a warning.
In chapters 9 and 10, Hebrews compares the inadequacy of the Old Testament sacrifices with the perfection and permanence of Christ's sacrifice in the New Testament. Because the Levitical system only prefigured Christ's one time sacrifice for sin, there was no longer any need of the Old Testament sanctuary and its rituals after He died.
In Hebrews 10:26-31 above, the author was warning Jewish Christians who were contemplating returning to Judaism that they faced "a terrifying expectation of judgment and the fury of a fire.
In other words, if a professed believer first embraces then rejects the way of escape the Father has provided, he has "insulted the Spirit of grace" and trampled the Son of God under foot, which leaves him no place to hide from God's wrath. All he has to look forward to is judgment at the hands of the living God - a terrifying prospect.
See The Wrath of God
When the both Testaments equally emphasize the love of God and the reality and terror of God's wrath, it is sad to find so many professing Christians who, perhaps because it makes them uneasy, either completely ignore everything the Scriptures says about the wrath of God, wish there were no such thing, or treat it as something for which they need to make an apology. Perhaps, deep down they believe that God's wrath is not consistent with His goodness - a blot on the Divine character if you will. Thus they see Him solely as a God whose one ambition is to keep us happy - and heaven forbid that He should ever cause us any grief. This large-scale rejection of the doctrine of the wrath of God and the emphasis placed almost exclusively upon His love is prime evidence that much of the modern church has separated itself from Christianity as taught by the Bible.
What and Where is Heaven?
Christians who believe they will spend an eternity in "heaven", seem to have little or no idea where this heaven is, what it will look like, or what they will do there. Either they have fleeting, half formed ideas about some ethereal place 'out there', or resort to pious phrases that amount to little more than spiritual gobbledy gook. If this is the best we can do then it is little wonder that non Christians are not in the slightest bit interested in our "heaven", and Christians themselves so rarely seem to look forward to the coming of the day of God. Luckily the Bible isn't at all silent on where "heaven" is and, even more importantly, what it will be like. In fact, the Bible's description of the coming kingdom is far, far, more practical than that of our theologians.
What and Where is Hell?
The belief that Hell is a place of unending torment has been so strongly held throughout the history of Christianity that few have dared to challenge it. Besides which, since most modern challenges have come from the cults, a person who dares to question the traditional viewpoint runs the risk of being labeled a cultist. However, the deeper one delves into the subject the less persuasive the argument in favor of the traditional view become. For example, there is not a single verse in the entire Bible that says anything remotely similar to "everyone has eternal life; it is only a matter of where each will spend it." Yet, this is what most of the church believes, assuming that the idea has its origins in the Bible. It does not. The Bible tells us that God alone possesses immortality. Additionally, Christians routinely take the word "death" to mean eternal life in hell, and the word "perish" to mean "never perish".
PART II - Understanding How The Bible Defines Sin HERE
If you do not know or accurately understand how the Bible defines sin, then you have absolutely no idea what it is that separates you from God, and why He will not hear you. It is also imperative to know and thoroughly understand what it takes to receive forgiveness of sins i.e. escape the death penalty and have eternal life in God's promised kingdom.
 Wayne Jackson. Christian Courier. A Realistic Look at Sin. http://www.christiancourier.com/articles/458-a-realistic-look-at-sin
 Cathy Lynn Grossman, USA Today. Has the 'notion of sin' been lost? http://www.usatoday.com/news/religion/2008-03-19-sin_N.htm
 Albert Mohler. Has the Notion of Sin Disappeared? http://www.albertmohler.com/2008/03/25/has-the-notion-of-sin-disappeared/