There are a number of Arabic words in Quran that refer to sin like: إِثْم and ذَنب and سَيِّئَة.
I am looking for the difference between them and their usage.
"دنب" originally means: "following something constantly" which is why tail is called "دنب" because it constantly follows the animals.
sin is called "ذنب" because the negative impact of committing sins constantly follows the sinner.
"اثم" originally means: "deceleration, slowing down and delay"
sin is called "اثم" because it decelerates our move in the straight way toward the perfection. It slows us down and causes a long delay on our trip toward All-Mighty Allah.
"سیئه" originates from "سوء" which means: "evil" and is the opposite of "good" . In Arabic this form of word (فعیل) is called "صفت مشبه" which implies a constant meaning. For instance, "رحیم" is someone who is constantly compassionate and merciful in contrast to "راحم" which is not implying the meaning of a constant compassion and mercy.
Therefore, sin is called "سیئه" because it is a constant evil.
There's an answer here that sais in short: http://fatwa.islamweb.net/fatwa/index.php?page=showfatwa&Option=FatwaId&Id=13700
فالسيئة هي: ما يسوء الإنسان في دنياه أو آخرته، قال تعالى: (وَإِنْ تُصِبْكُمْ سَيِّئَةٌ يَفْرَحُوا بِهَا) [آل عمران:120].
so سَيِّئَة is soething bd that happens to the person
Then الخطيئة is when you do something wrong without 'knowing about it'. for example بَلَى مَنْ كَسَبَ سَيِّئَةً وَأَحَاطَتْ بِهِ خَطِيئَتُهُ means when someone does something bad to some people, and that bad thing has consequences after his act finished (like nudity: something that becomes fashionable, and people adopt it for generations)
The word ذَنب means the tail, so it is equivalent to khati2a (even though I don't beleive it is, there must be good arabic doctors who know the difference even if it is subtile). The proof it is not the same is that it is used as two distinct words in the same eya here : (وَمَنْ يَكْسِبْ خَطِيئَةً أَوْ إِثْماً) (here I'm NOT translating, since they say in the translation the opposite thing: they are next to each other so they are the same)
Finally they say that إِثْم is the evil action and ذَنب are the consequences of that bad action (their tail)