The dictionary lists multiple meanings for the word sin. The first meaning is to act immorally, contrary to divine law. Man's application of this is not clear or uniform, however, as highly educated and well-meaning people are miles apart in their actions. As an example, one may allow himself to speak in the library while another only allows whispering.
The second meaning listed is to commit an offense against God. Although people disagree as to what constitutes such an offense, the Bible believer has a source of knowledge and the possibility of further understanding and enlightenment on the subject. If we start with the premise that the Bible is true and has genuine integrity because it is originally inspired by God, then as Biblical students we can begin to build a very clear understanding of what has taken place when a person has sinned.
Consider the original sin. Despite the tempting and deceptive conversation introduced by the serpent, the final result was simple and plain; Adam and Eve's sin was failing to live up to the instructions given to them by God. This is evident in Genesis 3 as God asks Adam:
...Hast thou eaten of the tree, whereof I commanded thee that thou shouldest not eat? Genesis 3:11
If what it means to sin can be understood that simply, is it still the same today? And why do we still fall for it? In Matthew and I John we see that living according to God's instructions is not burdensome or drudgery.
For my yoke is easy, and my burden is light. Matthew 11:30
For this is the love of God, that we keep his commandments: and his commandments are not grievous. 1 John 5:3
Our world introduces the idea that life is difficult and complicated. We need not give in to that deception. God is not too good to be true, He's so good he is true. We just need to do our part by learning and heeding God's instructions. We elevate our living up to the level of God's Word and live above the drudgery of sin.
Thy word have I hid in mine heart, that I might not sin against thee. Psalm 119:11
And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God. Romans 12:2
But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you. Romans 6:17