Burglary (also called breaking and entering and sometimes housebreaking) is a crime the essence of which is entry into a building for the purposes of committing an offence. Usually that offence will be theft, but most jurisdictions specify others which fall within the ambit of burglary. Commission of burglary is normally referred to as to burgle (in British English) or burglarize (in American English).
Occasionally this element is expressed as the intent to commit a felony “therein”. The use of the word “therein” adds nothing and certainly does not limit the scope of burglary to those wrongdoers who break and enter a dwelling intending to commit a felony on the premises. [Boyce & Perkins, 3rd Ed., 269, citing ''People v. Wright'', 206 Cal.App.2d 184, 23 Cal.Rptr. 734 (1962)] The situs of the felony does not matter, and burglary occurs if the wrongdoer intended to commit a felony inside at the time he broke and entered. [Id.]
Jurisdictions often vary the common law elements of burglary. This common law definition has been expanded in most jurisdictions, such that the building does not need to be a dwelling or even a building in the conventional sense, physical breaking does not need to occur, the entry does not need to occur at night, and the intent may be to commit any felony or theft.
The etymology originates from Anglo-Saxon or Old English, one of the Germanic languages. According to one textbook, "The word burglar comes from the two German words berg, meaning "house," and laron, meaning "thief" (literally "house thief"). However, berg (as in Helderberg) technically means "mountain," and its burg (as in Harrisburg) actually means "town" or ""hilltop fortess," and thus from there, "house."
Burglary is prosecuted as a felony or misdemeanor, and involves trespassing and theft, entering a building or automobile, or remaining unlawfully with intent to commit theft or any crime, not necessarily a theft for example, vandalism. Even if nothing is stolen in a burglary, the act is a statutory offense. Burglary may be an element in crimes involving rape, arson, kidnapping, identity theft, or violation of civil rights; indeed the "plumbers" of the Watergate scandal were technically burglars. As with all legal definitions in the U.S., the foregoing description may not be applicable in every jurisdiction, since there are 50 separate state criminal codes, plus Federal and territorial codes in force.
Under Florida State Statutes, "burglary" occurs when a person unlawfully enters or remains in a dwelling, a structure, or a conveyance to commit therein, unless he or she remains in the dwelling, structure, or conveyance to commit a forcible felony. In essence, burglary is trespass when, at the time of the trespass, the perpetrator had the intention of committing an offense in the location. Depending on the circumstances of the crime, burglary can be classified as third-, second-, or first-degree felonies, with maximum sentences of five years, fifteen years, and life, respectively.
The acts of burglary and the intended crime, if carried out, are treated as separate offenses. Burglary is a felony, even when the intended crime is a misdemeanor, and the intent to commit the crime can occur when one "enters or remains unlawfully" in the building, expanding the common law definition. It has three degrees. Third-degree burglary is the broadest, and applies to any building or other premises. Second-degree burglary retains the common-law element of a dwelling, and first-degree burglary requires one to be in a dwelling and to be armed with a weapon or to cause injury. A related offense, criminal trespass, covers unlawful entry to buildings or premises without the intent to commit a crime, and is a misdemeanor or, in the third degree, a violation. Possession of burglar's tools, with the intent to use them to commit burglary or theft, is a misdemeanor.
In the criminal code of New Hampshire, "A person is guilty of burglary if he enters a building or occupied structure, or separately secured or occupied section thereof, with purpose to commit a crime therein, unless the premises are at the time open to the public or the actor is licensed or privileged to enter."
Under the penal law in New York, burglary is always a felony, even in third degree. It is more serious if the perpetrator uses what appears to be a dangerous weapon, or if he or she enters a dwelling. 
In many jurisdictions in the U.S., burglary occuring at night is punished more severely than burglary occuring at other time. In California, nighttime burglary was punished as burglary in the first degree, while daytime burglary was punished as burglary in the second degree. California now distinguishes between entry into a residence and into a commercial building, with the burglary into a residence with heavier punishment.
In states that continue to punish nighttime burglary more severely than daytime burglary and burglary which occurred during twilight, night is defined as hours between 30 minutes after sunset and 30 minutes before sunrise.
Possession of burglar's tools, in jurisdictions that make this an offense, has also been viewed as an inchoate crime:
Burglary is defined by section 9 of the Theft Act 1968 which created two variants:
Although physical evidence of entry is not normally difficult to obtain, it can be difficult on occasions to decide whether an entry has occurred in law. In R v Collins, it was held that entry had to be "substantial" and "effective". The issue arose in R v Brown 1985 71 Cr App R 15 in which the defendant had been found on the pavement outside a shop with the top half of his body through the broken window, sorting though property on display for sale; this was held by the Court of Appeal to constitute an effective entry, while regarding the use of the word "substantial" as unnecessarily wide. It was ruled that the jury had been entitled to conclude that the entry had been effective. Furthermore, in R v Ryan 1996 160 JP 610, the defendant had been found partially within a building, having been trapped by a window, and argued that this was not a sufficient entry. However, he was convicted as it was held that a partial entry was sufficient and that it was irrelevant that he was due to circumstances incapable of stealing anything.
The Theft Act 1968 does not define a building, so this must be a matter of fact for the jury, however Section 9(3) specifically states that the term includes an "inhabited vehicle or vessel"; hence motor homes, caravans and houseboats are protected by the section even when temporarily unoccupied. Burglary can also be committed in "part of a building" and in R v Walkington 1979 1 WLR 1169 the defendant had entered a large shop during trading hours but went behind a counter and stole money from a till. The court held that he had entered that part of the building normally reserved for staff as a trespasser and was therefore guilty of burglary.
The essence of trespass is entering or remaining another's property without authority; a person having permission to enter property for one purpose who in fact enters for another purpose may become a trespasser, and in R v Jones and Smith, a defendant who had a general permission to enter his father's home became a trespasser when he did so in order to steal a television set, because doing so was inconsistent with the general permission. In recent years, the terms "distraction burglary", "artifice burglary" and "burglary by trick" have been used in crime prevention circles when access to premises is granted as a result of some deception on the occupier, usually by a pretence that the burglar represents some body who might reasonably request access such as a water, gas or electricity supplier.  There is no separate legal definition of this variant.
The intention to commit an offence, being an essential element of burglary, requires proof beyond reasonable doubt. For example, if entry is made to regain property which the defendant honestly believes he has a right to take, there is no intention to steal and the defendant is entitled to be acquitted. However, it has been held that a conditional intent to steal anything found to be of value is enough to satisfy this requirement.
R v Collins is authority for the proposition that the defendant must at least be reckless as to whether his entry is a trespass. For the Section 9(1)(a) offence, proof beyond reasonable doubt is required that the defendant intended to commit the offence specified as part of the burglary. In the Section 9(1)(b) offence, the mens rea is that of the offence committed, such that, for example, if grievous bodily harm is inflicted, recklessness will be sufficient to establish liability.
The maximum penalty for burglary is 14 years imprisonment if committed in a dwelling and 10 years otherwise. Section 4 of the Crime (Sentences) Act 1997 specifies a minimum 3 year prison sentence for third-time domestic burglary unless exceptional circumstances apply. Higher courts have consistently upheld lengthy custodial sentences for burglaries of dwellings; see, for example R v Brewster 1998 1 Cr App R (S) 181
In R v Kelt 1977 65 Cr App R 74 it was held that this phrase will normally mean mean "carrying", and in R v Klass 162 JP 105, The Times, 17 December 1997 (CA) others had entered a building for criminal purposes while the defendant remained outside, but in possession of a scaffolding pole which had been used to break a window. This did not, in law, constitute an entry for the purposes of burglary. It was held that since Klass had not himself entered the building, he was guilty of burglary and not aggravated burglary.
It is necessary to prove that the defendant was aware of his possession of a weapon to convict of aggravated burglary. In R v Russell 1984 Crim L R 425, the defendant was found in possession of a knife but had forgotten that he had it; it was held that he was not guilty of aggravated burglary. A plea that the defendant did not intend to use the weapon is not a defence to this charge (R v Stones 1989 1 WLR 156).
Under Scots law in Scotland the crime of burglary is called theft by housebreaking. It does not include any other aspect of burglary. Housebreaking when combined with other crimes is considered acquisitive crime. It is a crime usually prosecuted under solemn procedure.
In Canada, burglary is labelled as "Breaking and Entering" under section 348 of the Criminal Code and is a hybrid offence. Breaking and entering is defined as trespassing with intent to commit an indictable offence. The crime is commonly referred to in Canada as "break and enter".  
In Sweden, burglary does not exist as an offence in itself, instead there are two available offences. If a person simply breaks into any premise, he is technically guilty of either unlawful intrusion or breach of domiciliary peace (olaga intrång and hemfridsbrott), depending on the premise in question. Breach of domiciliary peace is only applicable when a person "unlawfully intrudes or remains where another has his living quarters". The only punishment available for any of these offences is fines, unless the offence is considered gross. In that case, the maximum punishment is two years in prison.
However, if the person who has forced himself into a house, steals anything (literally "takes what belongs to another with intent to acquire it"), he is guilty of (ordinary) theft (stöld). However, the section regarding gross theft (Chapter 6, 4s of the Penal Code, grov stöld) states "in assessing whether the crime is gross, special consideration shall be given to whether the unlawful appropriation took place after intrusion into a dwelling." For theft, the punishment is imprisonment of at most two years, while gross theft carries a punishment of between six months and six years.