Bail,  in English common law, the freeing or setting at liberty of one arrested or imprisoned upon any action, either civil or criminal, on surety taken for his appearance on a certain day and at a place named. The surety is termed bail, because the person arrested or imprisoned is placed in the custody of those who bind themselves or become bail for his due appearance when required. So he may be released by them if they suspect that he is about to escape and surrendered to the court, when they are discharged from further liability. The sureties must be sufficient in the opinion of the court, and, as a rule, only householders are accepted; in criminal cases the solicitor or an accomplice of the person to be bailed, a married woman or an infant would not be accepted. Bail is obligatory in all summary cases. It is also obligatory in all misdemeanours, except such as have been placed on the level of felonies, viz. obtaining or attempting to obtain property on false pretences, receiving property so obtained or stolen, perjury or subornation of perjury, concealment of birth, wilful or indecent exposure of the person, riot, assault in pursuance of a conspiracy to raise wages, assault upon a peace-officer in the execution of his duty or upon any one assisting him, neglect or breach of duty as a peace-officer, any prosecution of which the costs are payable out of the county or borough rate or fund.
In cases of treason, bail can only be granted by a secretary of state or the king's bench division. A person charged with felony is not entitled as of right to be released on bail. The power of admitting a prisoner to bail is discretionary and not ministerial, and the chief consideration in the exercise of that discretion must be the likelihood of the prisoner failing to appear at the trial. This must be gauged from the nature of the evidence in support of the accusation, the position of the accused and the severity of the punishment which his conviction will entail, as well as the independence of the sureties. The Bail Act 1898 gives a magistrate power, where a person is charged with felony or certain misdemeanours, or where he is committed for trial for any indictable offence, to dispense with sureties, if in his opinion the so dispensing will not tend to defeat the ends of justice. A surety may be examined on oath as to his means, while the court may also require notice to be given to the plaintiff, prosecutor or police.
A person who has been taken into custody for an offence without a warrant, and cannot be brought before a court of summary jurisdiction within twenty-four hours, may be admitted to bail by a superintendent or inspector of police; and in a borough, if a person is arrested for a petty misdemeanour, he may be bailed by the constable in charge of the police-station. Bail in civil matters, since the abolition of arrest on mesne process, is virtually extinct. It took the form of an instrument termed a bail-bond, which was prepared in the sheriff's office after arrest, and executed by two sufficient sureties, and the person arrested.
In admiralty proceedings in rem, bail is often required for procuring the release of arrested ships or cargo. It is also given without the arrest of the ship, as a substitution of personal security for that of the res, generally in an amount to cover the claim and costs.
In the United States, bail (in a sum fixed by the committing magistrate) is a matter of right in all cases where a sentence of death cannot be inflicted (Rev. Stat. § 1015). In those where such a sentence can be inflicted, it may be allowed by one of the judges of the United States courts at his discretion (ibid. § 1016).
 The ultimate origin of this and cognate words is the Lat. bajulus, properly a bearer of burdens or porter, later a tutor or guardian, and hence a governor or custodian, from which comes "bailiff"; from bajulare is derived the French bailler, to take charge of, or to place in charge of, and "bail" thus means "custody," and is applied to the person who gives security for the appearance of the prisoner, the security given, or the release of the prisoner on such security.