Shall' is a modal verb that is used to express obligation, necessity, or determination. It is often used in legal documents and contracts to indicate that something is required or expected. It is also used in everyday language to express a strong sense of obligation or determination. In some cases, it can be used interchangeably with 'WILL, ' but in other cases, the two words have different meanings. For example, 'shall' is used to express a stronger sense of obligation than 'WILL.'