Any thought, word, deed, or omission contrary to God's eternal law. All actual sins are classified on the basis of this division, where sinful thoughts are essentially desires, the words may either be spoken or otherwise articulated, the deeds involve some external manifestation, and omissions are failures to do what should have been done by a person in a given set of circumstances.
Sin is a human act that presumes three elements: objective malice in the action performed, or at least the person considers it wrong; actual advertence of mind by which the sinner is at least confusedly aware of the malice of his conduct; and consent of the will, which formally constitutes actual sin and without which the sin is said to be only material.
Every sin is a genuine offense against God. There is consequently no such thing as merely philosophical sin, which offends against right reason but is not at the same time a deliberate transgression of the divine law. Sin is theological by its very nature.