Key Scripture:

whatever is not of supernatural belief and trust is sin. Romans 14:23b

Whoever does miss the mark (sin) also does lawlessness, for sin is lawlessness. * 1 John 3:4

Owe no one anything, but to love one another: for whoever loves another has fulfilled the law.  For this: You shall not commit adultery, You shall not kill, You shall not steal, You shall not bear false witness, You shall not covet--and if there is any other commandment, it is briefly comprehended in this utterance, namely, You shall love your neighbor as yourself.  Love works no ill to his neighbor: therefore love is the fulfilling of the law.  And that, knowing the time, that now it is high time to awake out of sleep: for now is our salvation nearer than when we believed.  The night is far spent, the day is at hand: let us therefore cast off the works of darkness, and let us put on the armor of light.  Let us walk honestly, as in the day; not in wild parties and drunkenness, not in adultery and lasciviousness, not in zealous contention.  But put on the Lord Jesus Christ, and do not make provision into the flesh, to fulfill the desire for forbidden things.  Romans 13:8-14

Beloved, let us love one another: for love is of God; and everyone who loves is born of God, and knows God.  He who does NOT love, does NOT know God; for God is love. 1 John 4:7-8

Definitions:

Below are several definitions. In general, sin falls into three categories. 1. Slipping across the line. 2. Stepping across the line. 3. Missing the target.

Slipping across the line is simply the fruit springing as a result of the evil seeds that we have planted in the past, or they may even be the fruit of original sin we were born with because of the fall and what we inherited from Adam and Eve. We reap what we sow. The line is the law of God, which is more than the ten commandments. It includes the ten commandments and is summed up in one word, love. Stepping across the line usually follows slipping across the line. Some emotion, passion, anger, fear, feeling, or lust causes us to slip across the line, then we make a bad situation worse by stepping across the line. Perhaps someone whom God has set into authority makes a mistake, and the result is not fair to you. So you slip across the line and feel anger and disrespect for the person set by God (a parent, boss, elder, etc.). Then, you step across the line and say something you should not have said. That would be one of many possible examples. Missing the target accounts for much of sin. Missing the target is simply not listening to the voice of God or somehow in God's process of doing His righteousness through you, short-circuiting the process and missing the target. Here are a couple examples: God tells you, tell your spouse that you are sorry, and you don't do it. God shows you, by the Spirit, a higher level of order (the one in Scripture) for the church, but you have a lot to lose as a salaried pastor, so you choose to ignore the leading of God. This also is likely to include stepping across the line as you try to change Scripture to fit what you want to do.

• God has a good plan for you, to attain to God's glory. In your current condition, you have not received all that God has for you. To miss all of this glory is sin. Sin brings you out of the glory of God, step by step. Righteousness brings you into the glory of God, step by step.
• Sin is the reason for death and suffering. Had Adam never sinned, there would be no death and no suffering. The Bible tells us that the last enemy to be defeated will be death. Sin brings you into death and out of life, step by step. Righteousness brings you into life and out of death, step by step.
• Sin and death are the two things from which Jesus came to set us free.
• Rebellion, wanting to be autonomous from God, separates us from God. When we are separated from God, we cannot be godly--how would it be possible to be godly? When we are separated from God, we miss out on His glory, His leading, and His power for righteousness.
• The lack of love is sin. This is another way of saying the same thing.
• Disobeying the commandment of God is sin. God's commandment is to love. Adultery, Fornication, Stealing, Lying, Cheating, Envying, Killing; these are all examples of a lack of love.
• A desire to NOT glorify and respect God and NOT hold Him in holy reverence is sin.
• A desire to add to and take away from God's Word and to follow one's own mind and will is sin, which leads to spiritual death and is the cause of physical misery, sickness, and death.

The path toward the fulfillment of what God intends to do in our lives is opened by being joined to God. We can only be joined through Jesus. We need forgiveness. We need to bridge the gap. We cannot possibly do it ourselves. Even our righteousness is as filthy rags to God. God had to make the ultimate sacrifice to win us back to Himself.
Sin "may be regarded as the missing of a mark or aim." ~ Archbishop Trench

See also: What Is Sin?

Below are some some literal translations of the words that are used in the Bible for sin:

Hamartia or hamartano: Straying from the path.
Parabasis: Stepping across
Paraptoma: Slipping across
Anomia: Lawlessness, disregarding God's law
Opheilema: Debt

51 αγνοημα agnoema ag-no'-ay-mah
from 50; TDNT-1:115,18; n n
AV-error 1; 1
1) a sin committed through ignorance or thoughtlessness {#Heb 9:7}

93 αδικια adikia ad-ee-kee'-ah
from 94; TDNT-1:153,22; n f
AV-unrighteousness 16, iniquity 6, unjust 2, wrong 1; 25
1) injustice, of a judge
2) unrighteousness of heart and life
3) a deed violating law and justice, act of unrighteousness

264 αμαρτανω hamartano ham-ar-tan'-o
perhaps from 1 (as a negative particle) and the base of 3313; TDNT-1:267,44; v
1) to be without a share in
2) to miss the mark
3) to err, be mistaken
4) to miss or wander from the path of uprightness and honour, to do or go wrong
5) to wander from the law of God, violate God's law, sin

266 αμαρτια hamartia ham-ar-tee'-ah
from 264; TDNT-1:267,44; n f
1) equivalent to 264
1a) to be without a share in
1b) to miss the mark
1c) to err, be mistaken
1d) to miss or wander from the path of uprightness and honour, to do or go wrong
1e) to wander from the law of God, violate God's law, sin
2) that which is done wrong, sin, an offense, a violation of the divine law in thought or in act
3) collectively, the complex or aggregate of sins committed either by a single person or by many

265 αμαρτημα hamartema ham-ar'-tay-mah
from 264; TDNT-1:267,44; n n
1) sin, evil deed
For Synonyms see entry 5879

458 ανομια anomia an-om-ee'-ah
from 459; TDNT-4:1085,646; n f
AV-iniquity 12, unrighteousness 1, transgress the law + 4160 1, transgression of the law 1; 15
1) the condition of without law
1a) because ignorant of it
1b) because of violating it
2) contempt and violation of law, iniquity, wickedness
For Synonyms see entry 5879

677 απροσκοπος aproskopos ap-ros'-kop-os
from 1 (as a negative particle) and a presumed derivative of 4350; TDNT-6:745,946; adj
AV-void of offense 1, none offense 1, without offense 1; 3
1) having nothing to strike against, not causing to stumble
1a) of a smooth road
1b) metaph. of not leading others to sin by one's mode of life

763 ασεβια asebeia as-eb'-i-ah
from 765; TDNT-7:185,1010; n f
AV-ungodliness 4, ungodly 2; 6
1) want of reverence towards God, impiety, ungodliness

2275 ηττημα hettema hayt'-tay-mah
from 2274;; n n
AV-diminishing 1, fault 1; 2
1) a diminution, decrease: i.e. defeat
2) loss, as respects to salvation

3845 παραβαινω parabaino par-ab-ah'-ee-no
from 3844 and the base of 939; TDNT-5:736,772; v
AV-transgression 3, fall by transgression 1; 4
1) to go by the side of
2) to go past or pass over without touching a thing
3) to overstep, neglect, violate, transgress
4) so to go past as to turn aside from

3847 παραβασις parabasis par-ab'-as-is
from 3845; TDNT-5:739,772; n f
AV-transgression 6, breaking 1; 7
1) a going over
2) metaph. a disregarding, violating
2a) of the Mosaic law
2b) the breach of a definite, promulgated, ratified law
2c) to create transgressions, i.e. that sins might take on the character of transgressions, and thereby the consciousness of sin be intensified

3876 παρακοη parakoe par-ak-o-ay'
from 3878; TDNT-1:223,34; n f
AV-disobedient 3; 3
1) a hearing amiss
2) disobedience

3892 παρανομια paranomia par-an-om-ee'-ah
from the same as 3891; TDNT-4:1090,646; n f
AV-iniquity 1; 1
1) breach of law, transgression, wickedness
For Synonyms see entry 5879

3900 παραπτωμα paraptoma par-ap'-to-mah
from 3895; TDNT-6:170,846; n n
AV-trespass 9, offense 7, sin 3, fall 2, fault 2; 23
1) to fall beside or near something (to fall or slip aside)
2) a lapse or deviation from truth and uprightness
2a) a sin, misdeed

4348 προσκομμα proskomma pros'-kom-mah
from 4350; TDNT-6:745,946; n n
AV-stumbling stone + 3037 2, stumbling block 2, stumbling 1, offense 1; 6
1) a stumbling block
1a) an obstacle in the way which if one strikes his foot against he stumbles or falls
1b) that over which a soul stumbles i.e. by which is caused to sin

4625 σκανδαλον skandalon skan'-dal-on ("scandal")
probably from a derivative of 2578; TDNT-7:339,1036; n n
AV-offense 9, stumbling block 3, occasion of stumbling 1, occasion to fall 1, thing that offends 1; 15
1) the movable stick or trigger of a trap, a trap stick
1a) a trap, snare
1b) any impediment placed in the way and causing one to stumble or fall, (a

0205 ןוא 'aven aw-ven'
from an unused root perhaps meaning properly, to pant (hence, to exert oneself, usually in vain; n m; {See TWOT on 48 @@ "48a"}
AV-iniquity 47, wicked( ness) 8, vanity 6, affliction 3, mischief 3, unrighteous 2, evil 1, false 1, idol 1, mourners 1, mourning 1, nought 1, sorrow 1, unjust 1, vain 1; 78
1) trouble, wickedness, sorrow
1a) trouble, sorrow
1b) idolatry
1c) trouble of iniquity, wickedness

0819 "משׁא 'ashmah ash-maw'
from 0817; TWOT-180c; n f
1) guiltiness, guilt, offense, sin, wrong-doing
1a) doing wrong, committing a trespass or offense
1b) becoming guilty, guilt
1c) bringing a guilt-offering

0817 םשׁא 'asham aw-shawm'
from 0816; n m; {See TWOT on 180 @@ "180b"}
AV-trespass offering 34, trespass 8, offering for sin 1, sin 2, guiltiness 1; 46
1) guilt, offense, sin, guiltiness
1a) offense, sin, trespass, fault
1b) guilt, guiltiness
1c) compensation (for offense)
1d) trespass or sin offering

01942 "ו" havvah hav-vaw'
from 01933; n f; {See TWOT on 483 @@ "483a"}
AV-calamity 4, wickedness 3, perverse thing 1, mischief 1, noisome 1, iniquity 1, substance 1, naughtiness 1, naughty 1, mischievous 1; 16
1) desire
1a) desire (in bad sense)
2) chasm (fig. of destruction)
2a) engulfing ruin, destruction, calamity

02401 "אט-- chata'ah khat-aw-aw'
from 02399; TWOT-638d; n f
1) sin, sin offering
1a) sin
1b) sin offering

02403 "אט-- chatta'ah khat-taw-aw' or תאט-- chatta'th khat-tawth'
from 02398; TWOT-638e; n f
1) sin, sinful
2) sin, sin offering
2a) sin
2b) condition of sin, guilt of sin
2c) punishment for sin
2d) sin-offering
2e) purification from sins of ceremonial uncleanness

02398 אט-- chata' khaw-taw'
a primitive root; TWOT-638; v
1) to sin, miss, miss the way, go wrong, incur guilt, forfeit, purify from uncleanness
1a) (Qal)
1a1) to miss
1a2) to sin, miss the goal or path of right and duty
1a3) to incur guilt, incur penalty by sin, forfeit
1b) (Piel)
1b1) to bear loss
1b2) to make a sin-offering
1b3) to purify from sin
1b4) to purify from uncleanness
1c) (Hiphil)
1c1) to miss the mark
1c2) to induce to sin, cause to sin
1c3) to bring into guilt or condemnation or punishment
1d) (Hithpael)
1d1) to miss oneself, lose oneself, wander from the way
02399 ajx chet' khate
from 02398; TWOT-638a; n m
1) sin
1a) sin
1b) guilt for sin
1c) punishment for sin

02399 אט-- chet' khate
from 02398; n m; {See TWOT on 638 @@ "638a"}
AV-sin 30, faults 1, grievously 1, offenses 1; 33
1) sin
1a) sin
1b) guilt for sin
1c) punishment for sin

04383 לושׁכמ mikshowl mik-shole' or לשׁכמ mikshol mik-shole'
from 03782; n m; {See TWOT on 1050 @@ "1050c"}
AV-stumblingblock 8, offense 2, ruins 2, offend 1, fall 1; 14
1) a stumbling, means or occasion of stumbling, stumbling block
1a) stumbling, fall
1b) means or occasion of stumbling, stumbling block

04604 לעמ ma'al mah'- al
from 04603; n m; {See TWOT on 1230 @@ "1230a"}
AV-trespass 17, transgression 6, trespassed 2, falsehood 1, grievously 1, sore 1, very 1; 29
1) unfaithful or treacherous act, trespass
1a) against man
1b) against God

05512 ןיס Ciyn seen
of uncertain derivation;; n pr loc
AV-Sin 6; 6
Sin =" thorn" or "clay"
1) a town in eastern Egypt
2) the tract of wilderness between Elim and Sinai

05753 "וע 'avah aw-vaw'
a primitive root; v; {See TWOT on 1577}
AV-iniquity 4, perverse 2, perversely 2, perverted 2, amiss 1, turn 1, crooked 1, bowed down 1, troubled 1, wickedly 1, wrong 1; 17
1) to bend, twist, distort
1a) (Niphal) to be bent, be bowed down, be twisted, be perverted
1b) (Piel) to twist, distort
1c) (Hiphil) to do perversely
2) to commit iniquity, do wrong, pervert
2a) (Qal) to do wrong, commit iniquity
2b) (Hiphil) to commit iniquity

05766 לוע 'evel eh'- vel or לוע 'avel aw'- vel and (fem.) "לוע 'avlah av-law' or "לוע 'owlah o-law' or "לע 'olah o-law'
from 05765; n m/f; {See TWOT on 1580 @@ "1580a"} {See TWOT on 1580 @@ "1580b"}
AV-iniquity 36, wickedness 7, unrighteousness 3, unjust 2, perverseness 1, unjustly 1, unrighteously 1, wicked 1, wickedly 1, variant 2; 55
1) injustice, unrighteousness, wrong
1a) violent deeds of injustice
1b) injustice (of speech)
1c) injustice (generally)

05771 ןוע 'avon aw-vone' or ןווע 'avown (#2Ki 7:9; Ps 51:5) aw-vone'
from 05753; TWOT-1577a; n m
1) perversity, depravity, iniquity, guilt or punishment of iniquity
1a) iniquity
1b) guilt of iniquity, guilt (as great), guilt (of condition)
1c) consequence of or punishment for iniquity06586 עשׁפ pasha' paw-shah'

a primitive root [identical with 06585 through the idea of expansion]; v; {See TWOT on 1846}
AV-transgress 17, transgressor 9, rebelled 6, revolt 6, offended 1, transgression 1, trespassed 1; 41
1) to rebel, transgress, revolt
1a) (Qal)
1a1) to rebel, revolt
1a2) to transgress
1b) (Niphal) to be rebelled against

06588 עשׁפ pesha' peh'- shah
from 06586; n m; {See TWOT on 1846 @@ "1846a"}
AV-transgression 84, trespass 5, sin 3, rebellion 1; 93
1) transgression, rebellion
1a1) transgression (against individuals)
1a2) transgression (nation against nation)
1a3) transgression (against God)
1a3a) in general
1a3b) as recognized by sinner
1a3c) as God deals with it
1a3d) as God forgives
1a4) guilt of transgression
1a5) punishment for transgression
1a6) offering for transgression

05932 "ולע 'alvah al-vaw'
for 05766; n f; {See TWOT on 1580 @@ "1580b"}
AV-iniquity 1; 1
1) injustice, unrighteousness, iniquity

05999 למע 'amal aw-mawl'
from 05998; n m/f; {See TWOT on 1639 @@ "1639a"}
AV-labour 25, mischief 9, misery 3, travail 3, trouble 3, sorrow 2, grievance 1, grievousness 1, iniquity 1, miserable 1, pain 1, painful 1, perverseness 1, toil 1, wearisome 1, wickedness 1; 55
1) toil, trouble, labour
1a) trouble
1b) trouble, mischief
1c) toil, labour

06588 עשׁפ pesha' peh'- shah
from 06586; n m; {See TWOT on 1846 @@ "1846a"}
AV-transgression 84, trespass 5, sin 3, rebellion 1; 93
1) transgression, rebellion
1a1) transgression (against individuals)
1a2) transgression (nation against nation)
1a3) transgression (against God)
1a3a) in general
1a3b) as recognized by sinner
1a3c) as God deals with it
1a3d) as God forgives
1a4) guilt of transgression
1a5) punishment for transgression
1a6) offering for transgression

07562 עשׁר resha' reh'- shah
from 07561; n m; {See TWOT on 2222 @@ "2222a"}
AV-wickedness 25, wicked 4, iniquity 1; 30
1) wrong, wickedness, guilt
1a) wickedness (as violence and crime against civil law)
1b) wickedness (of enemies)
1c) wickedness (in ethical relations)

05753 "וע 'avah aw-vaw'
a primitive root; v; {See TWOT on 1577}
AV-iniquity 4, perverse 2, perversely 2, perverted 2, amiss 1, turn 1, crooked 1, bowed down 1, troubled 1, wickedly 1, wrong 1; 17
1) to bend, twist, distort
1a) (Niphal) to be bent, be bowed down, be twisted, be perverted
1b) (Piel) to twist, distort
1c) (Hiphil) to do perversely
2) to commit iniquity, do wrong, pervert
2a) (Qal) to do wrong, commit iniquity
2b) (Hiphil) to commit iniquity

05766 לוע 'evel eh'- vel or לוע 'avel aw'- vel and (fem.) "לוע 'avlah av-law' or "לוע 'owlah o-law' or "לע 'olah o-law'
from 05765; n m/f; {See TWOT on 1580 @@ "1580a"} {See TWOT on 1580 @@ "1580b"}
AV-iniquity 36, wickedness 7, unrighteousness 3, unjust 2, perverseness 1, unjustly 1, unrighteously 1, wicked 1, wickedly 1, variant 2; 55
1) injustice, unrighteousness, wrong
1a) violent deeds of injustice
1b) injustice (of speech)
1c) injustice (generally)

07686 "'שׁ shagah shaw-gaw'
a primitive root; TWOT-2325; v
1) to go astray, stray, err
1a) (Qal)
1a1) to err, stray
1a2) to swerve, meander, reel, roll, be intoxicated, err (in drunkenness)
1a3) to go astray (morally)
1a4) to commit sin of ignorance or inadvertence, err (ignorantly)
1b) (Hiphil)
1b1) to lead astray
1b2) to lead astray, mislead (mentally)
1b3) to lead astray (morally)

Sin "may be regarded as the missing of a mark or aim: it is then αμαρτια or αμαρτημα; the overpassing or transgressing of a line: it is then παραβασις; the disobedience to a voice: in which case it is παρακοη; the falling where one should have stood upright: this will be παραπτωμα; ignorance of what one ought to have known: this will be αγνοημα; diminishing of that which should have been rendered in full measure, which is ηττημα; non-observance of a law, which is ανομια or παρανομια."