In the New Testament, the Greek word generally translated "grace" is charis
definitions for charis:
1. a winning quality or attractiveness that invites a favorable reaction, graciousness, attractiveness, charm, winsomeness . . .
2. a beneficent disposition toward someone, favor, grace, gracious care/help, goodwill . . .
3. practical application of goodwill, (a sign of) favor, gracious deed/gift, benefaction . . .
2. a beneficent disposition toward someone, favor, grace, gracious care/help, goodwill . . .
3. practical application of goodwill, (a sign of) favor, gracious deed/gift, benefaction . . .
4. exceptional effect produced by generosity, favor. . . .
5. response to generosity or beneficence, thanks, gratitude
When referring to God's grace given to sinning humans, it is defined as God's benevolent attitude toward mankind. This attitude results in favor being granted by God to man. God's grace is wholly undeserved by mankind; it has not been (and cannot be) earned.
ROMANS 5:12 Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned - 13 for sin indeed was in the world before the Law was given, but sin is not counted where there is no Law. 14 Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come. 15 But the free gift is not like the trespass. For if many died through one man's trespass, much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many. 16 And the free gift is not like the result of that one man's sin. For the judgment following one trespass brought condemnation, but the free gift following many trespasses brought justification [dikaioma]. 17 If, because of one man's trespass, death reigned through that one man, much more will those who receive the abundance of grace [charitos] and the free gift of righteousness [dikaiosunes] reign in life through the one man Jesus Christ. 18 Therefore, as one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men. 19 For as by the one man's disobedience the many were made sinners, so by the one man's obedience the many will be made righteous 20 Now the Law came in to increase the trespass, but where sin increased, grace [charis] abounded all the more, 21 so that, as sin reigned in death, grace [charis] also might reign through righteousness leading to eternal life through Jesus Christ our Lord.
ROMANS 3:19 Now we know that whatever the Law says, it says to those who are under the Law, that every mouth may be stopped, and all the world may become guilty before God. 20 Therefore by the deeds of the Law no flesh will be justified in His sight, for by the Law is the knowledge of sin
GALATIANS 5:16 I say then: Walk in the Spirit, and you shall not fulfill the lust of the flesh. 17 For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, so that you do not do the things that you wish. 18 But if you are led by the Spirit, you are not under the Law. 19 Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness, 20 idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, 21 envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God. 22 But the fruit of the Spirit is love, joy, peace, longsuffering, kindness, goodness, faithfulness, 23 gentleness, self-control. Against such there is no law. 24 And those who are Christ's have crucified the flesh with its passions and desires. 25 If we live in the Spirit, let us also walk in the Spirit.
God's grace doesn't nullify the Law, but rather it voids the penalty we deserve for breaking the Law