Strictly speaking, an abettor is anyone who assists or encourages another person to do something. In criminal law, where the word is most commonly used, it is someone who assists or encourages another to commit a crime, usually by providing information, money, concealment, or some other item critical to the commission of the act. Abetting is a criminal offense, punishable by law. In some jurisdictions, the person assisting the criminal can be accorded the same sentence as the criminal himself.

The role of an abettor varies. Financing a criminal enterprise, assisting a criminal to elude capture, and driving a get-away car may all be considered abetting, depending on the jurisdiction and specific circumstances of the crime. Other examples of abetting can include instigating or inciting a crime, providing a false alibi, and furnishing the weapon used in the commission of a criminal act.

Abetting can occur before, during, or after the actual crime. The abettor need not be physically present at the scene of the crime and, in fact, usually is not. This person may have specific knowledge of the crime, or may simply know that a crime will be, or has been, committed. As long as the person's actions contribute to the commission of the crime, the person can be charged.

An abettor may be called by another name, depending on the jurisdiction and nature of the offense. Accomplice, instigator, and co-conspirator are other terms commonly used to describe someone who assists a criminal. In many cases, the difference between these terms is the level of the assistant's involvement in the crime. For example, a person who provides a robber with the layout of a bank, the security codes, and the combination to the vault, but does not actually take part in the physical robbery, may be an accomplice or co-conspirator; whereas a person who has no prior knowledge of the crime, but allows the robber to hide in her home afterwards so that the police cannot find him, may be an abettor.

Common charges related to abetting include aiding and abetting, abetting the commission of a crime, aiding and abetting a felon, and criminal abetting. A prosecutor might seek conviction on a lessor charge of abetting if he feels he does not have enough evidence to convict someone as an accomplice or co-conspirator, or if mitigating circumstances are present. An abetting conviction may be punishable by fines, community service, and/or jail time.