Planning a crime is not considered a crime in itself, but it can be illegal if it involves specific actions or agreements to commit a criminal act. Simply thinking about committing a crime is not illegal, but taking steps towards carrying it out can be considered a criminal offense.
Planning a Crime and Committing the crime
Not only is it considered a crime, it IS a crime. Felony is a synonym for crime.
No it is not considered a violent crime.
Adultery is not considered a crime in Arizona.
Adultery is not considered a crime in Illinois.
Suicide is not considered a crime in California.
No. It is not a crime.
Adultery is not considered a crime in New York.
Conspiracy, which involves planning with others to commit a crime, is illegal in modern society. It is considered a criminal offense and can result in serious legal consequences.
Without quoting California Penal Code Section 31, elements that would directly make one a principal to a crime, would be the direct involvement to committing a crime, or the direct involvement to aiding or abetting a crime by advice, coercion or counsel whether or not they are actually present.

 The Elements: o Planning o Preparation o And Carrying out the offense
Adultery is considered a crime in the states of Idaho, Michigan, Oklahoma, and Wisconsin.
Adultery is considered a crime in the states of Idaho, Michigan, Oklahoma, and Wisconsin.