Sin is any action, feeling, or thought that goes against God’s standards. It includes breaking God’s laws by doing what is wrong, or unrighteous, in God’s sight. (1 John 3:4; 5:​17) The Bible also describes sins of omission​—that is, failing to do what is right.​—James 4:​17.

 In the Bible’s original languages, the words for sin mean “to miss a mark,” or a target. For example, a group of soldiers in ancient Israel were so adept at slinging stones that they “would not miss.” That expression, if translated literally, could read “would not sin.” (Judges 20:16) Thus, to sin is to miss the mark of God’s perfect standards.

 As the Creator, God has the right to set standards for mankind. (Revelation 4:​11) We are accountable to him for our actions.​—Romans 14:12.

Is it possible to avoid sinning completely?

 No. The Bible says that “all have sinned and fall short of the glory of God.” (Romans 3:​23; 1 Kings 8:​46; Ecclesiastes 7:​20; 1 John 1:8) Why is that so?

 The first humans, Adam and Eve, were sinless in the beginning. That is because they were created perfect, in God’s image. (Genesis 1:​27) However, they lost their perfection by disobeying God. (Genesis 3:​5, 6, 17-​19) When they had children, they passed on sin and imperfection as inherited defects. (Romans 5:​12) As King David of Israel said, “I was born guilty of error.”​—Psalm 51:5.

Are some sins worse than others?

 Yes. For example, the Bible says that the men of ancient Sodom were “wicked, gross sinners” whose sin was “very heavy.” (Genesis 13:13; 18:20) Consider three factors that determine the gravity, or weight, of sin.

1.   Severity. The Bible warns us to avoid such serious sins as sexual immorality, idolatry, stealing, drunkenness, extortion, murder, and spiritism. (1 Corinthians 6:​9-​11; Revelation 21:8) The Bible contrasts these with thoughtless, unintentional sins, for example, words or actions that hurt others. (Proverbs 12:18; Ephesians 4:​31, 32) Nevertheless, the Bible encourages us not to minimize any sins, since they can lead to more serious violations of God’s laws.​—Matthew 5:​27, 28.

2.   Motive. Some sins are committed in ignorance of what God requires. (Acts 17:30; 1 Timothy 1:​13) While not excusing such sins, the Bible distinguishes them from sins that involve willfully breaking God’s laws. (Numbers 15:30, 31) Willful sins come from a “wicked heart.”​—Jeremiah 16:12.

3.   Frequency. The Bible also makes a distinction between a single sin and a practice of sin over an extended period. (1 John 3:​4-8) Those who “practice sin willfully,” even after learning how to do what is right, receive God’s adverse judgment.​—Hebrews 10:26, 27.

 Those guilty of serious sin can feel overwhelmed by the weight of their mistakes. For instance, King David wrote: “My errors loom over my head; like a heavy burden, they are too much for me to bear.” (Psalm 38:4) Yet the Bible offers this hope: “Let the wicked man leave his way and the evil man his thoughts; let him return to Jehovah, who will have mercy on him, to our God, for he will forgive in a large way.”​—Isaiah 55:7.