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 Oregon, burglary is defined under ORS 164.215 and 164.225. The state distinguishes between first-degree and second-degree burglary. Burglary in the first degree occurs when a person enters or remains unlawfully in a building with the intent to commit a crime therein and either: (1) the building is a dwelling, (2) the person has a burglary tool or theft device, or (3) the person commits the burglary intending to commit a theft or felony. Burglary in the second degree, a less severe offense, involves unlawfully entering or remaining in a building with the intent to commit a crime but without the aggravating factors required for first-degree burglary. Oregon law also recognizes the crime of possessing a burglary tool or theft device with the intent to use it (ORS 164.235). The distinction between burglary of a habitation and other buildings is significant, as burglary of a habitation is typically treated more seriously and carries greater penalties. The state does not specifically categorize the unlawful entry into vehicles, coin-operated machines, or ATMs as burglary, but such acts may fall under other criminal statutes related to theft or criminal mischief.