The word "sinned" in Romans in the Greek is "hamartano" and is spoken as (ham-ar-tan'-o; perh); meaning to "miss the mark (and so not share in the prize)."
Imagine if you are an archer, you shoot your arrow at the bull's eye; you either hit it or miss it. Well, that's what it is to sin, God has set the standard of life which by man can be right with him, and no one has hit the bull's eye.
There are some very clear guidelines within the Old and New Testament.
Laying out for mankind the benchmarks (base lines), which mankind should conduct their life by - they are absolutes from God,
Boundaries set by God Almighty, to live outside of these is sin, then there is the personal instructions God may give to and individual
whilst on the journey of life here on earth, to disregard these would be sin. i.e.. missing the mark God has set for you as an individual.
Romans 3:23
For all have sinned, and come short of the glory of God.
