In the name of allah, the Beneficent, the Merciful What is sin in Islam?

In the name of ALLAH, the Beneficent, the Merciful
What is sin in Islam?

The Holy Last Messenger (s.a.s.) said:

“Righteousness is good morality and sin is that which causes discomfort (or pinches) within your soul and which you dislike people to become informed of.” [Sahih Muslim]

Sin is that aspect in a Muslim’s life in which he or she makes effort to abstain from at all costs. Allah warns all of mankind that everything mankind does in this world will be put before us on Yawmul-Qiyaama (The Day of Resurrection) in Surah al-Zilzal:

“And he who does an atom’s weight of good will see it. And he who does an atom’s weight of evil will see it.” [Holy Qur’an, 99:7-8]

Allah also warns mankind that the one whose bad deeds (sins) are heavy will be in Hell, as can be found in Surah al-Qari’ah. A Muslim’s strife is to live the life of a believer and separate from the likeness of the sinner, as Allah differentiates the Mu’min (believer) from the fasiq (sinner) in Surah As-Sajdah:

“Is he who is a believer like unto him who is a sinner? They are not alike! For those who believe and do righteous works, for them are Gardens of Retreat, a welcome (in reward) for what works they did. And as for those who do evil, their abode is the Fire. Whenever they wish to leave, they will be forced back into it, and it will be said to them: Taste the torment of the Fire which you used to reject.” [Holy Qur’an, 32:18-20]

It is clear that one must steer away from sin and do righteous acts. However uncertainty arises in the mind when referring to the subject of sin such as;