Karetot 2: Meaning of Karet, When the Consequence is Karet

Our first Mishna outlines which prohibited actions, when done intentionally, is liable to karet*,  We learn that there are thirty-six cases that lead us to being punishment by karet:

• engaging in sexual intercourse with
• one's mother
• the wife of one's father even if she is not his mother 
• one's daughter
• another man
• one who has copulated with an animal
• a woman who has copulated with an animal
• a woman and her daughter
• a married woman
• one's sister
• one's father's sister
• one's mother's sister
• one's wife's sister
• one's brother's wife
• the wife of one's father's brother
• the wife of one's mother's brother
• a menstruating woman

• Karet is also the consequence for
• one who blasphemes the name of Heaven
• one who worships an idol
• one who gives one of his children to Molech, a different community's idol
• one who desecrates Shabbat
• one who is ritually impure and eats sacrificial food
• one who enters the Temple while ritually impure
• one who eats forbidden fat
• one who consumes blood
• one who eats meat left over from an offering time after notar, the time allotted for consumption
• one what eats meat of an offering that is piggul, sacrificed with the intent to consume it after its designated time
• one who one who slaughters and offers up these animals outside of the temple
• one who eats leavened bread on Pesach
• one who eats or performs prohibited labour on Yom Kippur
• One who blends the anointing oil just like Moshe did in the wilderness
• one who blends the incense according for purposes other than use on the temple
• one who applies annointing oil to one's skin
• one who does not fulfil the mitzvah of bringing the Paschal offering
• one who does not fulfil the obligation of circumcision
• these last two and different from the other reasons as they are positive mitzvoth
• We are reminded that regarding these sins, one is liable to receive karet for intentional violation and that we bring a sin offering for an unwitting violation
• When the violation's motivation is unknown, one is liable to bring provisional guilt offering provisional guild offering which provides provision al atonement until he learn whether or not he sinned
• Regarding sins that involve entering the Temple inappropriately, one must bring a sliding- scale offering for a definite transgression
• The Rabbi say that the halacha is the same regarding one who blasphemes, for "You shall have one law for him who performs the action unwittingly (Numbers15:29) excluding one who blasphemes and one who does not perform an action with sins but with speech

Each one of these cases is discussed at length.  Many of them include several categories, and others are combined to equal just one case of prohibited action.  The Gemara discusses some of these actions in detail.  As well, the rabbis note that when one might be liable for karet as well as another punishment, like lashes, and how this might be negotiated.  Finally, we learn that the rabbis are aware of the importance of witnesses in cases of karet - one must be seen transgressing by two people and one must be warned that the act is forbidden with a consequence of karet.

 * The meaning of karet is alternately defined as being forbidden from the world-to-come, ending one's life early - for example before 50, losing one's child, or having one's soul tortured in the world-to-come