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.

In Washington State, burglary is defined under the Revised Code of Washington (RCW) and is classified into different degrees based on the severity of the offense. The basic definition of burglary involves entering or remaining unlawfully in a building with the intent to commit a crime against a person or property therein. The most serious form, first-degree burglary (RCW 9A.52.020), occurs when a person enters or remains unlawfully in a dwelling with the intent to commit a crime and is armed with a deadly weapon or assaults any person therein. Second-degree burglary (RCW 9A.52.030) involves similar unlawful entry into a building other than a vehicle or dwelling, with criminal intent, but without the aggravating factors of a deadly weapon or assault. Residential burglary (RCW 9A.52.025) is a specific form of burglary that involves unlawfully entering or remaining in someone's dwelling with intent to commit a crime, regardless of whether the dwelling is occupied. Additionally, Washington recognizes burglary of a vehicle if the vehicle is a dwelling (such as an RV), or if the vehicle is equipped with a cargo area that is not accessible from the passenger area, and the crime involves the theft of property (RCW 9A.52.095). The state also has provisions for criminal trespass, which is a lesser offense than burglary and involves entering or remaining unlawfully on someone else's property without the intent to commit a crime.