Law & Grace - Define law for me

This is a test. What does law refer to in the book of Romans?

If I was asked by my professor to define a law, I would ask, which law? There are many laws - the law of gravity, the law of motion, laws of thermodynamics and laws of exponents just to name a few.
I grew up believing that I was not under the law but rather grace. I can say that I still believe this but would like to define the word law. I believe that when I accept Jesus that I am no longer under the law of sin & death or sin = death.
I do believe though that I am under the law (teaching/instruction) of God.
I start my study in Romans 6:14 which clearly states that this is referring to sin as the law -
For sin shall not be your master, because you are not under law, but under grace.
Man have I heard that so many times and thank the Lord because I need grace because all have fallen short.
I do recognize that I had taken this verse with the mindset that I was not held to the standards of the Old Testament because of grace and this is where my question lies.
Yes, I understand that the temple is gone. I understand that I am not in Jerusalem and I understand that I am not welcome in a synagogue but on the feast days and the commandments I do believe that they are for me. For one, the Bible will never contradict itself. If it says that I am free from the law in chapter 6 and chapter 7 v 12 says, So then, the law is holy, and the commandment is holy, righteous and good, I would say that I should define law in each specific reference.
More examples: 7:22 For in my inner being I delight in God's law; but I see another law at work in the members of my body, waging war and making me a prisoner of the law of sin...v25b So then, I myself in my mind am a slave to God's law, but in the sinful nature a slave to the law of sin.
We then see a new law presented in ch8. v2 because through Christ Jesus the law of the spirit of life set me free from the law of sin and death. This is the good stuff...v3 For what the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. And so he condemned sin in sinful man, in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the spirit. v7 the sinful mind is hostile to God. It does not submit to God's law, nor can it do so.
Quite a few laws and quite a few meanings. This verse just told me that the spirit of life in Christ Jesus enables me to submit to God's law. A revelation to me was that this law - God's law, the word law is translated from the Hebrew word meaning instructions. We can look at this two ways. As a child I did not like instructions, rules and guidelines but as I matured I began to see that when I knew the instructions I was able to win. God's law, God's instruction enables us to be that set apart people that are holy and useful to him. It enables us to win the race.
Paul goes on to state to the Romans in ch15 v 4 For everything that was written in the past (Old Testament) was written to teach us so that through endurance and the encouragement of the Scriptures (Old Testament) we might have hope. v8 For I tell you that Christ has become a servant of the Jews on behalf of God's truth to confirm the promises made to the patriarchs so that the Gentiles (that's me) may glorify God for his mercy, as it is written: "Rejoice, O Gentiles, with his people." Then to sum it up Paul tells us in Romans 15:16 to be a minister of Christ Jesus to the Gentiles with the priestly duty of proclaiming the gospel of God, so that the Gentiles might become an offering acceptable to God, sanctified by the Holy Spirit. Paul defines his ministry in v.18b as leading the Gentiles to obey God.