From the Adam's and Eve's experience, sin is any disagreement or contradiction with God or with His word in Moses and the Prophets.
God champions flawlessness, exactitude in even following instructions to the minute iota no matter at what cost (Hebrews 12:4). Think about the disagreement of Moses who was not allowed to set foot in Canaan that was to become the holy kingdom of Jesus, just because he failed to follow the instructions of Jesus! Just because of one instance, Jesus told Moses that he did not believe in Him! Numbers 20:11-12.
If we do not follow the instructions from Jesus or His commandments, we will not qualify to be a citizen of His kingdom.
Romans 5:14 ASV
(14) Nevertheless death reigned from Adam until Moses, even over them that had not sinned after the likeness of Adam's transgression, who is a figure of him that was to come.
Deuteronomy 32:48-52 ASV
(48) And Jehovah spake unto Moses that selfsame day, saying, (49) Get thee up into this mountain of Abarim, unto mount Nebo, which is in the land of Moab, that is over against Jericho; and behold the land of Canaan, which I give unto the children of Israel for a possession; (50) and die in the mount whither thou goest up, and be gathered unto thy people, as Aaron thy brother died in mount Hor, and was gathered unto his people: (51) because ye trespassed against me in the midst of the children of Israel at the waters of Meribah of Kadesh, in the wilderness of Zin; because ye sanctified me not in the midst of the children of Israel. (52) For thou shalt see the land before thee; but thou shalt not go thither into the land which I give the children of Israel.