The gill (pronounced/ˈdʒɪl/ ( listen)) or teacup is a unit of measurement for volume equal to a quarter of a pint. It is no longer in common use, except in regard to the volume of alcoholic spirits measures.
In Great Britain, the standard single measure of spirits in a pub was 1⁄6 gill (23.7 ml) in England, and 1⁄5 gill (28.4 ml) in Scotland; after metrication this was replaced by either 25 or 35 ml (0.176- or 0.246-gill) measures (landlords can choose which one to serve). The 1⁄4 gill was previously the most common measure in Scotland, and still remains as the standard measure in pubs in Ireland.
Half of a gill is a jack, so an eighth of a pint. But in northern England, a quarter pint could also be called a jack or a noggin rather than a gill, and in some areas a half pint could be called a gill, particularly for beer and milk.
In Ireland, the standard spirit measure was historically 1⁄4 gill. In the Republic of Ireland, it still retains this value, though it is now legally specified in metric units as 35.5 ml.