The expression 'Hong Kong Royal Instructions' is most commonly used to refer to the Hong Kong Royal Instructions 1917, one of the principal constitutional documents of British Hong Kong (others being the Hong Kong Letters Patent 1917, the Hong Kong Letters Patent 1960, the Hong Kong Letters Patent 1982, and the Hong Kong Letters Patent 1991 (No. 1)); however, it may also refer to any other Hong Kong Royal Instructions or any Hong Kong Additional Instructions ('Hong Kong Royal Instructions' amending the pre-existing Hong Kong Royal Instructions), or be used as a generic term covering all Hong Kong Royal Instructions and all Hong Kong Additional Instructions.