Oath in the context of "Vilnius Cathedral"

An oath of allegiance is an oath whereby a subject or citizen acknowledges a duty of allegiance and swears loyalty to a monarch or a country. In modern republics, oaths are sworn to the country in general, or to the country's constitution. For example, officials in the United States, take an oath of office that includes swearing allegiance to the United States Constitution. However, typically in a constitutional monarchy, such as in the United Kingdom, Australia, and other Commonwealth realms, oaths are sworn to the monarch. Armed forces typically require a military oath.

In feudal times, a person would also swear allegiance to their feudal superiors. To this day the oath sworn by freemen of the City of London contains an oath of obedience to the Lord Mayor of the City of London.

The Hippocratic Oath is an oath of ethics historically taken by physicians. It is one of the most widely known of Greek medical texts. In its original form, it requires a new physician to swear, by a number of healing gods, to uphold specific ethical standards. The oath is the earliest expression of medical ethics in the Western world, establishing several principles of medical ethics which remain of paramount significance today. These include the principles of medical confidentiality and non-maleficence. As the foundational expression of certain principles that continue to guide and inform medical practice, the ancient text is of more than historic and symbolic value. It is enshrined in the legal statutes of various jurisdictions, such that violations of the oath may carry criminal or other liability beyond the oath's symbolic nature.

The Shahada (Arabic: الشَّهَادَةُ aš-šahādatu; Arabic pronunciation: [aʃʃahaːdatʊ], 'the testimony'), also transliterated as Shahadah, is an Islamic oath and creed, and one of the Five Pillars of Islam and part of the Adhan. It reads: "I bear witness that there is no god but God, and I bear witness that Muhammad is the Messenger of God."The Shahada declares belief in the oneness (tawhid) of God and the acceptance of Muhammad as God's messenger. Some Shia Muslims also include a statement of belief in the wilayat of Ali, but they do not consider it as an obligatory part for converting to Islam. A single honest recitation of the Shahada is all that is required for a person to become a Muslim according to most traditional schools.

A military oath, also known as the oath of enlistment or swearing-in is an oath delivered by a conscript or volunteer upon enlisting into the state's armed forces. Various states have different phrasings of the oath, with the common component being the fidelity to the state and obedience to the superior officers. In the ancient times it was a very solemn procedure. In modern times, with many formal laws and regulations to maintain army discipline, it is still a solemn, but rather a formal event.

An oath of office is an oath or affirmation a person takes before assuming the duties of an office, usually a position in government or within a religious body, although such oaths are sometimes required of officers of other organizations. Such oaths are often required by the laws of the state, religious body, or other organization before the person may actually exercise the powers of the office or organization. It may be administered at an inauguration, coronation, enthronement, or other ceremony connected with the taking up of office itself, or it may be administered privately. In some cases it may be administered privately and then repeated during a public ceremony.

Some oaths of office are statements of allegiance and loyalty to a constitution or other legal text or to a person or office-holder (e.g., an oath to support the constitution of the state, or of loyalty to the king or queen) (see Oath of allegiance). Under the laws of a state, it may be considered treason or a high crime to betray a sworn oath of office. In many cases, the oath is performed using an oath book, typically religious scripture such as the Bible.

In law, a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know.

A witness might be compelled to provide testimony in court, before a grand jury, before an administrative tribunal, before a deposition officer, or in a variety of other legal proceedings. A subpoena is a legal document that commands a person to appear at a proceeding. It is used to compel the testimony of a witness in a trial. Usually, it can be issued by a judge or by the lawyer representing the plaintiff or the defendant in a civil trial or by the prosecutor or the defense attorney in a criminal proceeding, or by a government agency. In many jurisdictions, it is compulsory to comply with the subpoena and either take an oath or solemnly affirm to testify truthfully under penalty of perjury.

An affidavit (/ˌæfɪˈdeɪvɪt/ AF-ih-DAY-vit; Medieval Latin for "he has declared under oath") is a written statement voluntarily made by an affiant or deponent under an oath or affirmation which is administered by a person who is authorized to do so by law. Such a statement is witnessed as to the authenticity of the affiant's signature by a taker of oaths, such as a notary public or commissioner of oaths. An affidavit is a type of verified statement or showing, or containing a verification, meaning it is made under oath on penalty of perjury. It serves as evidence for its veracity and is required in court proceedings.

An oath of fealty, from the Latin fidelitas (faithfulness), is a pledge of allegiance of one person to another.