Paragraph 7. THE FALL

404
How did the sin of Adam become the sin of all his descendants? the whole human
race is in Adam “as one body of one man”.²⁹³ By this
“unity of the human race” all men are implicated in Adam’s sin, as
all are implicated in Christ’s justice. Still, the transmission of original sin
is a mystery that we cannot fully understand. But we do know by Revelation that
Adam had received original holiness and justice not for himself alone, but for
all human nature. By yielding to the tempter, Adam and Eve committed a personal
sin, but this sin affected the human nature that they would then transmit in a
fallen state.²⁹⁴ It is a sin which will be transmitted by propagation
to all mankind, that is, by the transmission of a human nature deprived of
original holiness and justice. and that is why original sin is called
“sin” only in an analogical sense: it is a sin “contracted”
and not “committed” – a state and not an act.

From The Catechism of the Catholic Church – rosary.team

Original Link: https://www.vatican.va/archive/ENG0015/__P1C.HTM