Electronic cigarettes or electronic nicotine delivery systems (ENDS) are devices that do not burn or use tobacco leaves but instead vaporize nicotine which the user then inhales. These products are most commonly referred to as e-cigarettes and using e-cigarettes is commonly referred to as ‘vaping’. Although some e-cigarettes look like conventional tobacco products (e.g. cigarettes, cigars, cigarillos, pipes, hookahs, or shishas), they may be produced in the form of everyday items such as pens, USB memory sticks and larger cylindrical or rectangular devices.

The other main constituents of the fluid besides nicotine are propylene glycol and vegetable glycerine. In addition, e-cigarette liquids and emissions usually contain other chemicals. E-cigarettes come in a variety of flavours.