A handbook is a type of reference work, or other collection of instructions, that is intended to provide ready reference. The term originally applied to a small or portable book containing information useful for its owner, but the Oxford English Dictionary defines the current sense as "any book...giving information such as facts on a particular subject, guidance in some art or occupation, instructions for operating a machine, or information for tourists." A handbook is sometimes referred to as a vade mecum (Latin, "go with me") or pocket reference. It may also be referred to as an enchiridion.