Inoculation (also known as variolation) was a historical method for the prevention of smallpox by deliberate introduction into the skin of material from smallpox pustules. This generally produced a less severe infection than naturally-acquired smallpox, but still induced immunity to it. The term entered medical English through horticultural usage meaning to graft a bud (or eye) from one plant into another. It is derived from the Latin in + oculus (eye). Though innoculation/innoculate is sometimes seen, this is incorrect, possibly erroneously thought to be related to innocuous, which is derive from the Latin in + nocuus (= not harmful).The terms inoculation, vaccination, immunization and injection are often used synonymously to refer to artificial induction of immunity against various infectious diseases. This is supported by some dictionaries. However, there are some important historical and current differences. In English medicine inoculation referred only to the prevention of smallpox until the very early 1800s. When Edward Jenner introduced smallpox vaccine in 1798 this was initially called cowpox inoculation or vaccine inoculation. Soon, to avoid confusion, smallpox inoculation was referred to as variolation (from variola = smallpox) and cowpox inoculation was referred to as vaccination (from Jenner's use of Variolae vaccinae = smallpox of the cow). Then, in 1891 Louis Pasteur proposed that the terms vaccine/vaccination should be extended to include the new protective procedures being developed. Immunization refers to the use of all vaccines but also extends to the use of antitoxin, which contains preformed antibody to e.g. diphtheria or tetanus exotoxins. Inoculation is now more or less synonymous in nontechnical usage with injection etc., and the question e.g. 'Have you had your flu injection/vaccination/inoculation/immunization?' should not cause confusion. The focus is on what is being given and why, not the literal meaning of the technique used.Inoculation also has a specific meaning for procedures done in vitro. These include the transfer of microorganisms into and from laboratory apparatus such as test tubes and petri dishes in research and diagnostic laboratories, and also in commercial applications such as brewing, baking and the production of antibiotics.In almost all cases the material inoculated is called the inoculum, or less commonly the inoculant, although the term culture is also used for work done in vitro.