A schooner is a type of glass for serving drinks. In Britain it is a large sherry glass (also known as a Sheila Glass), in Australia, it is a name for a particular glass size, used for any type of beer.
In South Australian pubs and clubs, the term "schooner" refers to a glass with a capacity of 285 mL (known as a "pot" elsewhere in Australia, and a "middy" in New South Wales and Western Australia 10 imp. fl. oz., or half an imperial pint, pre-metrication). In other Australian states "schooner" refers to a glass of 425 mL (15 imp. fl. oz., or three-quarters of an imperial pint, pre-metrication). It is the most common size in New South Wales, Queensland and the Northern Territory, although not unknown in other states. Currently, some hospitality venues in Western Australia are going through a process of "schoonerification", whereby the previous culture of drinking by pints has been changed with vessels of schooner size to allay increasing costs to venues and with encouragement from the state government to curb binge drinking.
In Canada, a "schooner" refers to a large capacity beer glass. Unlike the Australian schooner, which is smaller than a pint, a Canadian schooner is always larger. Although not standardized, the most common size of schooner served in Canadian bars is 32 oz. (946 mL); the volume of two US pints. It is usually a tankard (mug) shaped glass, rather than a pint shaped glass. It shouldn't be confused with Schooner Lager, which is a regional brand of beer found only in the eastern maritime provinces of Canada.
In Britain, a schooner is a large sherry glass. Sherry is traditionally served in one of two measures, based on how they were served in naval days. There was a clipper, the smaller measure, or a schooner, the larger measure, named after the sort of ships that brought sherry over from Spain. The schooner name was more particular to Bristol, to where most sherry was imported, stored and bottled. It is usually served on its own. Also since 2011 beer and cider is permitted to be sold in 2/3 pint (379ml) glasses known as 'schooners'.
Newcastle Brown Ale is traditionally served in a half-pint glass called a schooner, or 'Geordie schooner'.
In the United States, "schooner" refers to the shape of the glass (rounded with a short stem), rather than the capacity. It can range from 18 oz. (532 mL) to 32 oz. (946 mL).