Burglary is generally the unlawful entry of a building or structure to commit a felony criminal offense (crime), theft, or assault. The definition of burglary varies from state to state (and in the federal system), and some states have different degrees of severity of the burglary offense, depending on the nature of the unlawful entry (type of building or structure), the intended purpose, and the illegal action taken by the defendant once inside the building or structure. In some states, breaking into an automobile, a coin-operated machine, or an ATM (automated teller machine) with the intent to commit a theft may also constitute the crime of burglary.

A defendant generally commits the offense of burglary of a building or habitation (1) by entering a private habitation or any part of a building that was not open to the public, (2) without the consent of the owner, and (3) with the intent to commit a felony, theft, or assault.

A defendant may also commit the offense of burglary of a building or habitation by entering with consent, but remaining hidden with the intent to commit a felony, theft, or assault—or entering with consent and attempting to commit a felony, theft, or assault, or actually committing a felony, theft, or assault.

Some states make a distinction between burglary of a habitation (a place used for overnight accommodations) and burglary of a building that is not a habitation (home). Burglary of a habitation is usually treated as a more serious offense with greater penalties.

In Missouri, burglary is defined under Missouri Revised Statutes Section 569.160 and 569.170. The law distinguishes between first-degree and second-degree burglary. First-degree burglary, considered a more serious offense, involves entering a building or inhabitable structure unlawfully with the intent to commit a crime therein, and there is someone present in the structure, or the burglar is armed, threatens to use a deadly weapon, or causes or threatens to cause physical injury. Second-degree burglary is the unlawful entry into a building or inhabitable structure with the intent to commit a crime, but without the aggravating factors required for first-degree burglary. Missouri law also recognizes the crime of burglary of a habitation as more serious due to the invasion of the privacy and security of a person's home. Penalties for burglary in Missouri can be severe, with first-degree burglary being a Class B felony and second-degree burglary a Class D felony. The specific circumstances of the burglary, such as the type of structure and the defendant's actions, will influence the degree of the charge and the potential penalties upon conviction.