Dhanb is the most common word for ‘sin’ in the Qurʾān (37 times). After that is Ithm.
- O you who have believed, shall I guide you to a transaction that will save you from a painful punishment? [It is that] you believe in Allah and His Messenger and strive in the cause of Allah with your wealth and your lives. That is best for you, if you should know. He will forgive for you your sins and admit you to gardens beneath which rivers flow and pleasant dwellings in gardens of perpetual residence. That is the great attainment. And [you will obtain] another [favor] that you love - victory from Allah and an imminent conquest; and give good tidings to the believers. 61:10-13
Dhanb is a human fault, shortcoming, limitation, inadvertence, human error, mistake. The consequence of a Dhanb is a sanction or endorsement, rather than punishment or retribution.
Ithm is more serious. It’s a wilful transgression or deliberate disobedience. It requires punishment. It includes Dhanb, i.e. an Ithm can be conscious or unconscious. against Allāh or humanity.
Even more serious is fasiq?
a bad action, a step in the wrong direction, going off course. misdeed, bad action, wrong action
The concept of original sin does not exist in Islam. There is no inherent guilt from Adam’s expulsion from paradise.