An electronic cigarette (e-cig or e-cigarette), personal vaporizer (PV) or electronic nicotine delivery system (ENDS) is a battery-powered vaporizer which simulates the feeling of smoking, but without tobacco combustion. Their use is commonly called "vaping". The user automatically activates the e-cigarette by taking a puff; other devices turn on by pressing a button manually. They are often cylindrical, but come in many variations. Some e-cigarettes look like traditional cigarettes, but others do not. There are disposable cigalikes which are known as first generation "cigalikes" and there are reusable versions. Instead of cigarette smoke, the user inhales an aerosol, commonly called vapor. E-cigarettes typically have a heating element that atomizes a liquid solution known as e-liquid. E-liquids usually contain propylene glycol, glycerin, water, nicotine, and flavorings. E-liquids are also sold without propylene glycol, without nicotine, or without flavors.
Wikipedia: Electronic cigarette 。
