a. Sin is conduct unacceptable to the popular Christian community. Thus it does not include Sunday-keeping or Sabbath-breaking.
b. Sin is the transgression of the law--the standard SDA definition. Often superficially understood as mere breaking of a moral taboo. Much emphasis is on "known" acts of sin.
c. "Whatsoever is not faith is sin" or "sin is whatsoever is not of faith." (Remember the NT definition in No. 3). Sin is not the mere breaking of a taboo but a failure to appreciate Gods true character, revealed at the cross.